1 Mix the minced beef with the onion, season with salt and pepper and add the beaten egg. Shape into patties and flatten each one slightly.
2 Heat the oil in a frying pan and cook the burgers for 3-4 minutes on each side or until cooked through.
3 Cut 3 large circles and 14 small ones from the cheese slices. Make faces on the burgers using the sliced onion, gherkins, small cheese circles and crushed peppercorns for the 'eyes', the tomatoes for the 'noses' and mayonnaise and ketchup for the 'mouths'.
4 Place the lettuce leaves on the buns, add the hamburger faces and serve immediately.