Preheat the oven to 350°F. Prepare a baking sheet -- line it with parchment paper, aluminum foil or a silpat mat. Spray with cooking spray, and set aside.

In a large glass bowl, combine the ground turkey, cooked spinach, onion, garlic cloves, panko breadcrumbs, Parmesan, egg and spices using your hands.

When the meatball mixture has come together and is well mixed, prepare the meatballs. Using a small cookie scoop, form the meatballs with your hands, then place carefully on the baking sheet. Repeat the process until all the mixture has been made into meatballs.

Bake the meatballs for 30-40 minutes, or until browned on the outside and cooked through in the middle.

While the meatballs are baking, heat the olive oil in a Dutch oven over medium-high heat.

Add the onion and garlic, cooking for 2-3 minutes, or until the vegetables have become translucent.

Pour in the tomato puree and water, stirring until combined. Add the tomato paste and the spices, and bring to a boil.

Once at a boil, lower heat to a simmer and partially cover, simmering until the meatballs have finished cooking.

When the meatballs have finished cooking, transfer them directly into the marinara sauce.

Simmer the sauce and meatballs for an additional 30 minutes.

Toast the bread.

Slice the bread in half, and place the fresh mozzarella down first on the bottom slice.

Gently spoon meatballs and marinara sauce on top of the mozzarella, then top the sandwich with the other half of the bread.

Enjoy warm!