Steps
1. Preheat oven to 375°F (190°C).
2. In a bowl, mix cream cheese, mozzarella, cheddar, chopped spinach, and minced garlic. Season with salt and pepper.
3. Carefully cut a pocket into the side of the chicken breast without cutting all the way through.
4. Stuff the cheese and spinach mixture into the chicken pocket.
5. Secure with toothpicks if needed.
6. Heat olive oil in an oven-safe skillet over medium heat.
7. Sear chicken breast for 2-3 minutes on each side until golden.
8. Transfer skillet to the oven and bake for 20 minutes or until the chicken is cooked through.
9. Remove toothpicks before serving.