Steps
1. Preheat the oven to 375°F (190°C).
2. Cut a pocket into the side of the chicken breast.
3. Season the inside of the pocket with salt and pepper.
4. Stuff the pocket with chopped spinach and shredded mozzarella cheese.
5. Secure the opening with toothpicks.
6. Season the outside of the chicken breast with salt and pepper.
7. Place the chicken breast on a baking sheet.
8. Bake for 25-30 minutes or until the chicken is cooked through.
9. Remove the toothpicks before serving.