Preheat your oven to 400°F (200°C). Slice each chicken breast in half horizontally to create four thin cutlets. Pound the thicker ends to ensure even cooking.

In a bowl, mix together 1 tablespoon of olive oil, minced garlic, Italian seasoning, salt, and black pepper. Add the chicken cutlets to the marinade, cover, and refrigerate for 15-30 minutes.

In a skillet, heat the remaining tablespoon of olive oil over medium heat. Add the fresh spinach and sauté for 2-3 minutes until it wilts. Set aside.

In another bowl, beat the softened cream cheese until fluffy. Stir in the wilted spinach and 1/2 cup of mozzarella cheese. Add Parmesan cheese if using.

Arrange the chicken cutlets in a greased 9x13-inch baking dish. Spread the creamy spinach mixture over the chicken and top with the remaining mozzarella cheese.

Bake in the preheated oven for 20-30 minutes, until the chicken reaches 165°F (75°C) internally and the cheese is melted and lightly browned.

Allow the casserole to rest for about 5 minutes before serving.