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 mixing bowl, combine the ricotta, Parmesan, spinach, basil, garlic, nutmeg, salt, and pepper. Mix until all ingredients are 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, stopping before cutting all the way through to create a cavity for stuffing.
04 - Divide the ricotta filling evenly among the four chicken breasts, stuffing each pocket. Secure the opening with toothpicks if necessary to prevent filling from escaping during baking.
05 - Brush the outside of each stuffed breast with olive oil. Season evenly with salt and pepper on all sides.
06 - Place the stuffed breasts in the prepared baking dish, leaving space between each piece. Drizzle with remaining olive oil and sprinkle with Italian seasoning.
07 - Bake uncovered for 20 minutes, or until the chicken begins to turn golden brown.
08 - Remove from oven and top each breast with shredded mozzarella cheese. Return to oven and bake for an additional 10 minutes, until chicken reaches an internal temperature of 165°F and cheese is melted and golden.
09 - Let the chicken rest for 5 minutes before serving. Remove any toothpicks before plating.