01 - Preheat your oven to 400°F. Lightly grease a baking dish.
02 - Butterfly each chicken breast by slicing lengthwise through the thickest part, being careful not to cut all the way through. Open the breast like a book.
03 - Season both sides of the chicken breasts with salt and black pepper.
04 - In a bowl, combine ricotta, chopped spinach, parmesan, mozzarella, minced garlic, nutmeg, salt, and pepper. Mix well.
05 - Divide the spinach ricotta mixture evenly among the chicken breasts, spreading it over one side. Fold the other side over to enclose the filling.
06 - Secure the chicken breasts with toothpicks if needed. Place them in the prepared baking dish.
07 - Brush the tops with olive oil and sprinkle with remaining parmesan cheese.
08 - Bake for 25–30 minutes, or until the chicken is cooked through (internal temperature 165°F) and the tops are golden.
09 - Remove from oven, let rest 5 minutes. Remove toothpicks, slice, and serve.