Mix the ricotta and mozzarella cheeses together. Beat the eggs, then add them to the cheeses. Add in the salt, pepper, parsley, and nutmeg. Drop the shells in boiling water and boil them for 10 minutes. Drain the shells and cool them immediately with cold water. Grease the pan with butter. Put half the sauce in the bottom and on the sides of the pan. Stuff the shells with the cheese mixture. Put them cheese side down lined up in the pan. Pour the other half of the sauce over the top. Sprinkle the parmesan cheese on top of the sauce. Cover and bake at 350° for 45 minutes.