In a medium mixing bowl, combine the softened cream cheese, defrosted and squeezed spinach, sliced sun-dried tomatoes, garlic powder, shredded mozzarella, shredded Parmesan, and Italian seasoning; stir until evenly mixed.
Using a sharp knife, cut a pocket into the side of each chicken breast without cutting through to the other side.
Season the outside of each chicken breast and the inside of each pocket with salt and pepper, then sprinkle the outside with paprika.
Stuff each chicken pocket with the cream cheese mixture and secure the opening with a few wooden toothpicks.
Preheat the oven to 375°F (190°C).
Heat the olive oil and 1 tablespoon of sun-dried tomato oil in an oven-proof skillet over medium-high heat until shimmering.
Add the stuffed chicken breasts and cook until golden brown on the bottom, about 3–4 minutes; flip and brown the other side for 2–3 minutes.
Transfer the skillet to the preheated oven and bake 8–10 minutes more, or until the chicken is cooked through (no longer pink in the center).
Remove from the oven, let rest a few minutes, then remove toothpicks before serving.
