Season 4 pounds of ground steak with salt, pepper and onion juice, if desired. Dip hands in flour and mold meat into patties. Brush each side with sour-cream or with melted butter or margarine. Place on greased rack or in greased skillet and brown on both sides. Have ready buttered and toasted split buns. Spread with prepared mustard, if desired. Place patty and 1 slice of sweet onion between halves of the buns. Yield: 20 to 24 cakes.