Kidneys clean and soak for 2-3 hours in water, which is changed every 1 hour, then - another 2-3 hours in fresh milk. Drained, dry with a towel and cut into slices. Fry in very hot oil. Remove a latticed spoon and placed in a heated pan. The rest of the frying fat is boiled with wine, part of the butter and a pinch of salt, pepper and sugar. Chopped onion stew in the remaining butter, mix with the sauce of roasted and fuzzy starch in a little water and add to the boiling fat. The resulting sauce and stir once thickens, away from the fire. Serve in sauce-boat.