Knead the minced beef, egg and pepper and salt into the burgers. Brush the burgers with half of the oil and grill them on the barbecue for about 5 minutes per side.
Slice the onions into rings, fry them with the rest of the oil and salt in a frying pan until golden-brown.
Toast the hamburger rolls with the open side on the barbecue for a couple of minutes until light brown. Slice the tomatoes. Put the hamburgers and the sliced tomato and onions on the rolls. Secure with a skewer and place on a plate.
Fry the Private Reserve for 2½ to 3½ minutes at 175°C. Put them on the plate with the hamburger. Serve with hamburger sauce and coleslaw.