Season chicken breasts with salt and pepper to taste. Slit open on the side for stuffing; set aside.
In a medium bowl combine the ricotta, spinach, garlic, eggs and 3/4 of the cheese. Mix well and stuff each breast with 1/4 of the mixture; secure with toothpicks and place stuffed breasts in a lightly greased 20x30cm baking dish. Pour sauce over all and sprinkle with remaining cheese.
Bake for 45 to 60 minutes, or until chicken is cooked through and juices run clear.