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, chopped spinach, basil, minced garlic, nutmeg, salt, and pepper. Mix until thoroughly incorporated.
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 filling equally among chicken pockets. Secure openings with toothpicks to prevent filling from escaping during baking.
05 - Brush outside of each stuffed breast with olive oil. Season evenly with salt and pepper.
06 - Place stuffed chicken breasts in prepared baking dish. Drizzle with remaining olive oil and sprinkle with Italian seasoning.
07 - Bake uncovered for 20 minutes until chicken begins to brown.
08 - Remove from oven. Top each breast with shredded mozzarella. Return to oven for 10 minutes until internal temperature reaches 165°F and cheese is golden and bubbly.
09 - Let chicken rest for 5 minutes before serving. Remove toothpicks carefully before plating.