Lightly grease a casserole dish. Carefully slice each chicken breast horizontally to create two thinner cutlets, making a total of 4.
In a medium bowl, whisk together 1 tablespoon of olive oil, minced garlic, Italian seasoning, red pepper flakes, salt, and black pepper. Add the chicken cutlets, ensuring they are well-coated, and let them marinate for 15 minutes for enhanced flavor.
Preheat your oven to 400°F (200°C). In a skillet over medium heat, warm the remaining 1 tablespoon of olive oil. Add the spinach and gently cook for 3-5 minutes until just wilted, then set aside.
Remove the marinated chicken from the bowl, discarding any excess marinade, and arrange them evenly in your prepared casserole dish.
Spread the softened cream cheese evenly over each chicken cutlet. Layer the wilted spinach on top, followed by a generous sprinkle of shredded mozzarella cheese.
Bake for 25-30 minutes, or until the chicken is thoroughly cooked (internal temperature 165°F/74°C) and the cheese is bubbly and golden.