Preheat your oven to 400°F (200°C) and grease a 9x13-inch baking dish with olive oil.

Slice the chicken breasts horizontally into cutlets and pound them to even thickness, about half an inch.

Marinate the chicken in a mixture of olive oil, minced garlic, Italian seasoning, salt, and black pepper for 15-30 minutes.

Sauté the spinach in a skillet with olive oil for 2-3 minutes until wilted.

Beat the cream cheese until smooth and mix in the sautéed spinach and half of the shredded mozzarella cheese.

Optional: Sear the marinated chicken for 1-2 minutes per side in a hot skillet.

Assemble by arranging marinated chicken in the baking dish, spreading the creamy spinach mixture on top, and sprinkling remaining mozzarella cheese.

Bake for 20-30 minutes until chicken reaches 165°F (75°C) and cheese is melted and bubbly.

Let the casserole rest for 5 minutes before serving.