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

Cut chicken breasts horizontally to create thin cutlets and pound them gently.

Whisk together olive oil, minced garlic, Italian seasoning, salt, and black pepper. Coat chicken in this mixture and refrigerate for 15 to 30 minutes.

Heat remaining olive oil in a skillet over medium heat and sauté fresh spinach for 2 to 3 minutes until wilted.

Beat the cream cheese until smooth, then fold in the sautéed spinach and half of the shredded mozzarella cheese.

In the greased baking dish, place the marinated chicken in a single layer. Spread the cream cheese mixture over the chicken and top with remaining mozzarella.

Bake in the oven for 20 to 30 minutes until cheese is bubbly and golden brown, and chicken reaches an internal temperature of 165°F (75°C).

Let the casserole rest for about 5 minutes before serving.