Preheat the oven to 375 degrees.
Cut the chicken breasts in half, length wise, to create smaller fillets of chicken. Place each chicken breast into a sprayed 9x13 Pyrex pan. Sprinkle with 1/2 of the salt and pepper.
Over medium heat, add the garlic and spinach. Cook the spinach until it is cooked down, stirring frequently. Add the ricotta cheese and cook until the cheese is melted.
Scoop the ricotta mixture evenly on each of the chicken breasts in the Pyrex pan. Cover each chicken breast with the mozzarella cheese and cook for 20-25 minutes, or until the chicken is cooked through.