01 - Preheat your oven to 400°F. Lightly grease a baking dish large enough to hold the chicken breasts in a single layer.
02 - In a bowl, mix the ricotta, Parmesan, spinach, basil, garlic, nutmeg, salt, and pepper until well combined.
03 - Pat chicken breasts dry. Using a sharp knife, cut a pocket in the side of each breast, being careful not to cut all the way through.
04 - Stuff each chicken breast with an equal amount of the ricotta mixture. Secure with toothpicks if needed.
05 - Brush the outside of each breast with olive oil and season with salt and pepper.
06 - Place the stuffed breasts in the baking dish. Drizzle with the remaining olive oil and sprinkle with Italian seasoning.
07 - Bake uncovered for 20 minutes. Remove from oven, top each breast with mozzarella cheese, and return to oven for another 10 minutes, or until the chicken reaches an internal temperature of 165°F and the cheese is golden and bubbly.
08 - Let rest for 5 minutes before serving. Remove toothpicks before plating.