1/3 cup + 2 tablespoons freshly grated Parmesan cheese, divided
1/2 teaspoon kosher salt
1/4 teaspoon ground black pepper
3 cloves garlic, minced
1 egg, lightly beaten
2 tablespoons olive oil
4 ounces shredded mozzarella
minced fresh basil, for garnish
To make the sauce, heat olive oil in a large skillet pan over medium heat. Add onion and cook 1 minute. Stir in the tomato paste, garlic, parsley, basil, oregano and red pepper flakes and mix until fragrant, about 30 seconds. Add the crushed tomatoes, stir, lower heat to simmer and cook about 6 to 8 minutes, or until the sauce is thickened. Remove from heat and stir in the cream.
To make the meatballs, preheat the oven to 400 degrees F. In a large bowl, combine the ground chicken, spinach, bread crumbs, onion, 1/3 cup Parmesan cheese, salt, pepper, garlic and egg. Stir together with a fork then knead gently with your hands until evenly combined. Form the mixture into meatballs about 1 1/2 inches in diameter.
Heat olive oil in another medium or large skillet pan over medium-high heat. Add the meatballs to the pan in a single layer. Let cook, turning occasionally, until all sides are browned. (They will not be cooked all the way through because they will finish cooking when baked.) Place the meatballs in the pan with the tomato sauce. Sprinkle mozzarella and remaining 2 tablespoons Parmesan cheese over the top. Bake until the cheese is melted and the meatballs are cooked through, about 15 minutes. Remove from oven, garnish with fresh basil and serve.