Wash the heart, but do not let it soak, or stand in water. Fill it with a stuffing made of minced meat or of bread, either one of them seasoned with onion, sage, thyme, marjoram, pepper and salt, and an egg to bind it. Bake it for two hours, basting it frequently with water from the pan. When the heart is cooked remove it, and add to the pan a tablespoonful of flour; stir until it has browned. Then, if there is not enough liquor in the pan, add to it just enough water to make a thick sauce. Strain this over the heart, and serve on the same dish some boiled and browned onions.