Slice Chicken: Using a sharp knife, make a deep pocket in the thickest part of each chicken breast, being careful not to cut through the other side.
Season: In a small bowl, mix garlic powder, onion powder, smoked paprika, salt, and pepper. Rub the seasoning mixture all over the chicken breasts, including inside the pockets.
Prepare the Stuffing:
Mix Ingredients: In a medium bowl, combine the mozzarella (or cream cheese), spinach, sun-dried tomatoes, Parmesan cheese, and fresh herbs. Mix until well blended.
Stuff the Chicken: Divide the stuffing mixture into 4 equal portions. Spoon the mixture into the pockets of each chicken breast. Secure the opening with toothpicks, if necessary.
Cook the Chicken:
Sear the Chicken: Heat olive oil in a large oven-safe skillet over medium heat. Sear the stuffed chicken breasts for 2-3 minutes per side, until golden brown.
Bake: Transfer the skillet to the preheated oven and bake for 20-25 minutes, or until the internal temperature of the chicken reaches 165°F (74°C).
Serve:
Garnish: Remove toothpicks and serve hot, garnished with extra fresh herbs if desired.