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

Cut the boneless, skinless chicken breasts in half horizontally to create thinner cutlets. Pound the chicken to an even thickness using a meat mallet.

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

Sauté fresh spinach in olive oil over medium heat for 2-3 minutes until wilted, then set aside.

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

Optionally sear the marinated chicken in the skillet for 2-3 minutes on each side until slightly browned.

Assemble the casserole by layering marinated chicken cutlets at the bottom, spreading the creamy spinach mixture on top, and sprinkling the remaining mozzarella cheese above.

Bake in the preheated oven for 20-30 minutes until chicken reaches 165°F (75°C) and the cheese is bubbling and golden brown.

Let the casserole rest for about 5 minutes before serving.