Season a leg of mutton with salt, pepper and a pinch of cloves. Lay in a baking-pan with 1 sliced onion, 2 celery roots, 3 cloves of garlic and 2 carrots cut fine, 1 bay-leaf, a sprig of thyme and a few peppercorns. Pour over 1 cup of vinegar and 1 cup of hot water. Dredge with flour and let bake in a hot oven. Baste often with the sauce in the pan until nearly done; then add 1 pint of sour cream and let bake until done. Thicken with flour; boil up and pour over the roast.