Preheat the oven to 375°F (190°C). Grease a baking dish and set aside.

Using a sharp knife, carefully cut a pocket into each chicken breast without cutting all the way through.

In a small bowl, mix mozzarella cheese, cream cheese, spinach, sun-dried tomatoes, garlic, and red pepper flakes.

Stuff each chicken breast with the mixture and secure with toothpicks if necessary.

Season the outside of the chicken with salt, black pepper, garlic powder, onion powder, smoked paprika, and Italian seasoning.

Heat olive oil in a large oven-safe skillet over medium heat. Sear the chicken for 2-3 minutes per side until golden brown.

Transfer the skillet to the oven and bake for 18-22 minutes or until the chicken reaches an internal temperature of 165°F (75°C).

Remove from the oven, let rest for 5 minutes, then serve hot with a side of vegetables or salad.