Steps
1. Preheat your oven to 375°F (190°C).
2. In a bowl, mix together the chopped spinach, cream cheese, mozzarella cheese, minced garlic, Italian seasoning, salt, and pepper until well combined.
3. Using a sharp knife, create a pocket in the chicken breast by slicing it horizontally, being careful not to cut all the way through.
4. Stuff the cheese and spinach mixture into the pocket of the chicken breast, securing it with toothpicks if necessary.
5. Heat olive oil in an oven-safe skillet over medium-high heat. Sear the stuffed chicken breast for about 3-4 minutes on each side until golden brown.
6. Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (75°C).
7. Remove from the oven, let it rest for a few minutes, then slice and garnish with fresh parsley if desired. Serve hot.