Garlic Parmesan Mashed Potato Casserole

Garlic Parmesan Mashed Potato Casserole makes the PERFECT Thanksgiving and holiday side dish! Creamy russet potatoes are cooked with garlic cloves, then mashed with butter, milk and parmesan cheese. Top with additional parmesan before baking to create a crispy exterior on this comforting casserole. Makes 8 large servings.

Need something to pair this casserole with? Check out Browned Butter Sage Turkey and Brioche Bread Stuffing Recipe!

A close up of Garlic Parmesan Mashed Potato Casserole, shown in a purple baking dish with a serving spoon

This post first appeared at Julie’s Eats and Treats, where I was a contributor.

The night I made this casserole for the first time, my husband declared, “I think those are the best mashed potatoes you’ve ever made.”

And y’all, this is something coming from him because the man is not really a mashed potato fan.

In fact, he’s the great grandson of a rice farmer, so their family always ate rice with dinner. 

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    For him to be on board with a mashed potato dish is kind of a Big Deal.

    Why I love this recipe:

    This Garlic Parmesan Mashed Potato Casserole is my new favorite potato dish, too, because it is so very simple to make and 

    It also packs a ton of flavor into the potatoes and works as the perfect side dish for a special occasions, whether it’s a holiday meal OR a big family dinner. This is also lovely as a weeknight side dish, too.

    No matter when you serve this mashed potato casserole, it’s gonna be well-loved because it is the ULTIMATE comfort food.

    Please note that this is not a classic mashed potato casserole recipe, so you won’t find ingredients like sour cream, cream cheese, fresh chives or green onions here, but this is a fun twist on the classic.

    And the best news is Garlic Parmesan Mashed Potato Casserole can and should be made in advance so you don’t have to fret about it the day of! 

    I’ll tell you exactly how to do this a little farther down in this post, as well as in the recipe card. Promise.

    Other make-ahead Thanksgiving sides our whole family adores: Creamed Cornbread CasseroleBourbon Sweet Potato CasseroleFresh Green Bean CasseroleDrunken Cranberry Sauce

    Searching for Thanksgiving recipes that save the day every time? Check out my BEST Thanksgiving Recipes recipe index!

    Potatoes are shown sitting on a grey polka dot towel on an aqua background

    What do I need to make this recipe?

    The Speckled Palate participates in affiliate programs. As an Amazon Associate, I earn a commission from qualifying purchases. Please refer to my disclosure page for more information about these affiliate programs.

    Let’s talk ingredients!

    In addition to the tools above, you’re going to need some ingredients to make this recipe, too! Chances are, you might already have some of them in your fridge or pantry. Scroll down to the recipe card for the full measurements and instructions.

    Here’s what you need:

    • Potatoes — russet potatoes have a lot of starch, and because of this, they are the best potatoes for this recipe. They will break down as we boil them, which is what we want. I do not recommend using Yukon gold potatoes or pre-made mashed potatoes in this dish.
    • Garlic cloves — or granulated garlic / garlic powder, if you’re unsure if you’d like the garlic cooked with the potatoes
    • Kosher salt — or another medium-grain salt
    • Unsalted butter — you can also use salted butter if that’s what you’ve got on hand. If you make this swap, leave out the salt and give the potatoes a taste before seasoning.
    • Whole milk — while you can use another milk in this recipe, I really advise the whole milk because it will make the potatoes more flavorful.
    • Parmesan cheese — use your favorite parmesan. We like to shred our own, but I know the pre-shredded stuff can be a lot easier!
    • Black pepper

    Substitutions and additions:

    • Swap the parmesan for shredded cheddar cheese. 
    • Mix crunchy panko bread crumbs with the shredded cheese for extra crunchiness in the topping.
    • Add crispy bacon for a meaty crunch to the topping.
    Diced potatoes in water in a stock pot before cooking

    How to make Garlic Parmesan Mashed Potato Casserole

    First and foremost, scrub the potatoes!

    Next, peel the potatoes using a vegetable peeler. 

    Once peeled, chop into 1″ cubes using a sharp knife.

    Why? Because the smaller the cubes, the less time it’ll take for them to get soft. 

    Make the mashed potatoes

    To do this, we are going to follow my Homemade Mashed Potatoes recipe, but make them extra creamy. 

    First, fill a large pot with cold water. Add the potatoes and garlic to the water. Season with salt, and turn on the flame. (Don’t add potatoes to boiling water because they will cook unevenly.)

    Cooked potatoes are shown in a pot, surrounded by other ingredients used in Garlic Parmesan Mashed Potato Casserole

    Bring to a boil over high heat, and cook until the potatoes are fork tender.

    When the potatoes are tender, drain in a colander, and then put them back into the saucepan. Leave the garlic in, too, because that’s going to add immense flavor!

    Garlic Parmesan Mashed Potato Casserole is shown in a pot, just after mixing in all the ingredients, and before it is transferred to a baking dish to cook in the oven with additional cheese

    Measure the butter, milk and 1 cup of parmesan cheese on top of the potatoes

    Use a hand mixer or a potato masher to combine the ingredients until creamy and smooth (or your desired consistency if you like a chunkier potatoes.) 

    Season with salt and pepper.

    Please note that you can use leftover mashed potatoes here if you’ve got enough! 

    Garlic Parmesan Mashed Potato Casserole is topped with additional parmesan cheese before baking

    Bake the casserole

    Preheat the oven, and spray a baking dish with nonstick cooking spray.

    Transfer the creamy mashed potato mixture into the prepared dish

    Close up of Garlic Parmesan Mashed Potato Casserole before it goes into the oven to bake

    Sprinkle the additional shredded cheese on top.

    Bake uncovered for 25 minutes, then turn up the heat for an additional 15 minutes. This final 15 minutes in the higher heat is going to melt and brown the cheese. The baking time is dependent on your oven, so keep an eye on the dish, especially near the end so it does not burn.

    When the cheese is all bubbly, remove the casserole from the oven, and let it cool slightly. 

    If you’re making this on a holiday, and it needs to come out of the oven earlier, cover it with aluminum foil so it retains some heat!

    Serve warm, and enjoy.

    mashed potato casserole in a blue baking dish

    Erin’s Easy Entertaining Tips

    I loooooooooove casseroles for entertaining because they’re super easy to make in advance and super easy to store and reheat. 

    They’re also delicious.

    Here are a few of the things I’ve learned about this mashed potato casserole over the years that might help you as you make it to entertain your people:

    • Make it in advance. You can put this casserole together 2-3 days beforehand, and keep the dish covered in the fridge before you bake it on the day of your event.
    • Leave out the garlic if you don’t like it (or if your guests don’t, too). We adore garlic in our house because garlic adds amazing flavor… but I know not everyone’s tastebuds are like ours. If you’re skeptical or worried about using garlic, leave it out, and sprinkle some granulated garlic into the mashed potatoes along with the salt and pepper once you’ve whipped them up. Go by taste, and make your measurements confidently.
    • Keep it warm. This is a dish that you can make 1-2 hours in advance and cover with aluminum foil to ensure it stays warm. You don’t want it to be scorching hot when you serve it, so covering it will do the trick for a little bit!
    A serving of the potatoes is served on a white plate

    Frequently Asked Questions

    What is the best way to mash the potatoes?

    Personally, I like to use a hand mixer* (affiliate link) to make the mashed potatoes super smooth.

    The potatoes should be soft enough that they can very easily blend with the other ingredients.

    When the potatoes are fork tender, drain, then toss them back in the saucepan (or Dutch oven) with the butter, milk and parmesan. Blend slowly with the hand mixer and pick up speed as the ingredients meld together. Blend until whipped and silky smooth.

    Does this recipe use leftover mashed potatoes?

    If you happen to have 3 lbs. of mashed potatoes leftover, sure! Depending on how they were made, you might need to add a little more milk, butter, parmesan and garlic.

    With the garlic, I suggest cooking it in a pan with some olive oil or butter before throwing it into the potatoes so it’s not completely raw since raw garlic has a more potent taste than cooked.

    Can I make this Mashed Potato Casserole ahead of time?

    YES! In fact, I advise doing this because it makes life easier.

    Make the mashed potatoes a day or two before the big day, and transfer them into a baking dish. (You won’t cover them in cheese or bake now—that’ll come the day of!) All you’ll do now is cover them with plastic wrap, then store in the fridge.

    The day of, unwrap the casserole dish, top with cheese and bake until the cheese is golden, brown, bubbly and delicious.

    Can I make this casserole at home and transport it to another location without too much drama?

    YES! This dish would be awesome to transport and quite easy to finish at someone else’s house.

    Follow the instructions laid out about making the dish in advance. Bring it covered in plastic wrap, and once there, top with cheese and bake until bubbly and delicious.

    I don’t like fresh garlic. Can I use granulated garlic instead?

    Sure! I know fresh garlic can be a little strong for some, so if you want to make the swap, do it. I would start with ½ teaspoon of the granulated garlic. Taste it for flavor, and add more if you want more garlic flavor.

    a purple casserole dish holding a baked potato casserole with the text mashed potato casserole

    Quick tips and tricks for the best potato casserole:

    • Cook the mashed potatoes in advance, ​and assemble the casserole early, especially if you’re making this to serve as a side for Thanksgiving dinner, Christmas dinner or even a big family dinner.
    • Have fun with the flavors. ​If you like different cheese, give that a try!
    • How to store: Cover with foil or plastic wrap in the fridge and store for up to 5 days. If you have a smaller amount of casserole and want to remove it from the casserole dish, store in an airtight container.

    More potato recipes to try:

    Now who’s ready to make this life changing, make ahead mashed potato casserole?

    A close up of Garlic Parmesan Mashed Potato Casserole, shown in a purple baking dish with a serving spoon
    Yield: 8 large servings

    Garlic Parmesan Mashed Potato Casserole

    Prep Time: 15 minutes
    Cook Time: 1 hour
    Total Time: 1 hour 15 minutes

    Garlic Parmesan Mashed Potato Casserole makes the PERFECT Thanksgiving and holiday side dish! Creamy russet potatoes are cooked with garlic cloves, then mashed with butter, milk and parmesan cheese. Top with additional parmesan before baking to create a crispy exterior on this comforting casserole. No matter if you're serving the family for a holiday or on a weeknight, Garlic Parmesan Mashed Potato Casserole packs a flavorful punch for any meal!

    Ingredients

    • 3 lbs. russet potatoes, scrubbed, peeled and diced into 1” cubes
    • 5 garlic cloves, whole
    • 1 teaspoon kosher salt, (to season put in water for the diced potatoes)
    • 4 tablespoons unsalted butter
    • 1 cup whole milk
    • 1 ¾ cups parmesan cheese, shredded and divided
    • 1 teaspoon black pepper, freshly ground
    • ½ teaspoon kosher salt

    Instructions

    1. Using a sharp knife, chop the scrubbed and peeled potatoes into 1” cubes.
    2. Fill a large saucepan or Dutch oven with water, then add the potatoes to the water. Place the garlic cloves in the water, as well.
    3. Season the water with a teaspoon of salt.
    4. On the stovetop, heat the water and potatoes over high heat and bring to a boil. Cook until the potatoes are fork tender, about 20 minutes.
    5. Drain the potatoes, and place back in the saucepan.
    6. Measure out the butter, milk and 1 cup of parmesan cheese on top of the potatoes.
    7. Using a hand mixer on a low speed, slowly blend the ingredients together until smooth and creamy. Season the potatoes with salt and pepper.
    8. Preheat the oven to 350°F. Spray a baking dish with nonstick cooking spray, and set aside.
    9. Transfer the mashed potatoes into the prepared baking dish. Sprinkle the additional ¾ cup cheese on top of the casserole.
    10. When the oven is preheated, transfer the casserole to the oven.
    11. Bake for 25 minutes, then turn up the heat to 425°F. Bake for an additional 15 minutes, or until the cheese has browned.
    12. Remove from the oven, and let cool slightly.
    13. Serve warm, and enjoy!

    Notes

    Make Ahead Tip: Make the mashed potatoes a day or two before the big day, and transfer them into a baking dish. (You won’t cover them in cheese or bake now—that’ll come the day of!) All you’ll do now is cover them with plastic wrap, then store in the fridge.

    The day of, unwrap the casserole dish, top with cheese and bake until the cheese is golden, brown, bubbly and delicious.

    Nutrition Information:

    Yield:

    8

    Serving Size:

    1 serving

    Amount Per Serving: Calories: 311Total Fat: 12gSaturated Fat: 7gTrans Fat: 0gUnsaturated Fat: 4gCholesterol: 31mgSodium: 731mgCarbohydrates: 39gFiber: 4gSugar: 4gProtein: 12g

    Nutrition facts are an estimate and not guaranteed to be accurate.

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    About the Author:

    Erin Parker is a Southern gal living in Texas with her husband and two daughters. She started The Speckled Palate to share what she was cooking as a newlywed… and over the years, it’s evolved to capture her love for hosting. Specifically, the EASIEST, lowest key entertaining because everyone deserves to see their people and connect over good food. Learn more about her

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