01 - Preheat the oven to 400°F. Lightly grease a baking dish with olive oil or nonstick spray.
02 - In a mixing bowl, combine the chopped spinach, softened cream cheese, mozzarella, Parmesan, chopped sun-dried tomatoes, minced garlic, ¼ teaspoon salt, and ¼ teaspoon black pepper. Stir until all ingredients are evenly distributed.
03 - Using a sharp knife, slice a deep pocket into the thickest side of each chicken breast. Take care not to cut all the way through to the opposite side.
04 - Divide the spinach-cheese filling evenly among the four chicken breasts, spooning it into each pocket. Secure the openings with toothpicks if needed to keep the filling enclosed.
05 - In a small bowl, combine the Italian seasoning, paprika, ½ teaspoon salt, and ¼ teaspoon black pepper. Rub this seasoning blend over every surface of the stuffed chicken breasts.
06 - Heat 1 tablespoon of olive oil in a large ovenproof skillet over medium-high heat. Sear the stuffed chicken breasts for 2 to 3 minutes per side until a golden crust forms.
07 - Transfer the skillet directly into the preheated oven, or move the chicken to the prepared baking dish and drizzle with the remaining tablespoon of olive oil. Bake for 20 to 25 minutes until the internal temperature of the thickest breast reaches 165°F.
08 - Remove from the oven and discard any toothpicks. Let the chicken rest for 3 to 5 minutes before slicing and serving.