Preheat the oven to 350°F. Spray a 9”x13” baking pan with nonstick baking spray, and set aside. You may also line it with parchment paper to assist in lifting out the final bars.

In the bowl of a stand mixer using the flat beater attachment, cream the softened butter, granulated sugar and brown sugar together until the butter is light yellow and the sugars are well incorporated, about 2-3 minutes. Use a rubber spatula to scrape down the sides.

Add in the egg and vanilla extract, beating until combined, about 1-2 minutes. Scrape down the sides using the rubber spatula to ensure all ingredients get mixed in.

Measure the flour, salt and soda into the mixing bowl before turning on the mixer at a low speed. Continue mixing until the batter has come together and is nice and sticky.

Measure in the M&M candies, chocolate chips and sprinkles. Gently mix them into the batter using the flat beater attachment or a rubber spatula.

Scoop the cookie dough out of the bowl and into the prepared baking pan. Use your hands or an offset spatula to press the batter out evenly throughout the pan.

Bake for 30 minutes, or until golden brown and cooked through.

Let cool completely on a wire cooling rack before cutting into 24 cookie squares.

Enjoy with a glass of your favorite kind of milk!