01 - Preheat oven to 400°F. Lightly grease a baking dish large enough to hold chicken breasts in a single layer.
02 - In a mixing bowl, combine ricotta, Parmesan, spinach, basil, garlic, nutmeg, salt, and pepper. Mix thoroughly until evenly distributed.
03 - Pat chicken breasts dry with paper towels. Using a sharp knife, carefully cut a horizontal pocket in the side of each breast without cutting through completely.
04 - Divide ricotta mixture evenly among chicken pockets. Secure openings with toothpicks if necessary to prevent filling from escaping during cooking.
05 - Brush exterior of each breast with olive oil and season with salt and pepper. Place stuffed breasts in prepared baking dish. Drizzle with remaining olive oil and sprinkle with Italian seasoning.
06 - Bake uncovered for 20 minutes until chicken begins to brown and filling is heated through.
07 - Remove from oven. Top each breast with mozzarella cheese. Return to oven and bake additional 10 minutes until internal temperature reaches 165°F and cheese is golden and bubbly.
08 - Let chicken rest for 5 minutes before serving to allow juices to redistribute. Remove toothpicks before plating.