Preheat your oven to 400°F (200°C) and lightly grease a 9×13 inch baking dish.
Slice the chicken breasts horizontally into four cutlets and pound the thicker parts to even thickness.
In a large bowl, whisk together 1 tablespoon of olive oil, minced garlic, Italian seasoning, salt, and pepper. Coat the chicken with this mixture and refrigerate for 15-30 minutes.
Heat the remaining olive oil in a skillet over medium heat. Add spinach and cook until wilted, about 2-3 minutes. Set aside.
In a bowl, beat the softened cream cheese until smooth. Mix in the cooked spinach, half of the mozzarella, and Parmesan if using.
Remove chicken from marinade, letting excess drip off. Optionally, sear in the skillet for 1-2 minutes per side. Arrange in the baking dish.
Spread the spinach and cream cheese mixture over the chicken, then sprinkle with the remaining mozzarella.
Bake for 20-30 minutes until the chicken is cooked through and cheese is golden. Rest for 5 minutes before serving.
Notes
Feel free to swap any of the toppings or ingredients with what you have on hand. It will probably taste just as delicious!