Peel potatoes and boil in 500 milliliters of salted water until done, drain the water, mash potatoes into a puree. Peel apples, slice into pieces, stew with sugar and lemon juice for 15 minutes until potatoes seethe. Mix with mashed potatoes, season with salt, pepper and nutmeg. Place into the baking form and bake not long. Cut onion into circles, fry until golden brown, put onto potatoes, serve with the blood sausage.