In a large bowl, add the ground beef, sea salt and pepper. Mix well. Cover and chill in the fridge for 1 hour. Shape the mixture into 4 burgers.
Heat a frying pan or barbecue over high heat. Brush both sides of the burgers with oil. Cook for 3 to 4 minutes on each side until charred and cooked to your liking. Place a few slices of cheese on each burger and place the lid on the pan if frying, or place a stainless steel bowl over them if on a barbecue, to steam and melt the cheese.
Cook the pancetta slices until golden and crispy. Fry the duck eggs in hot oil until cooked to your liking. Toast the burger buns.
Mix the mayonnaise with the mustard and spread over the base of each bun.
Add some lettuce, tomato and red onion slices, followed by the burger, pancetta slice, fried egg and a good grating of black truffle and finally the other half of the bun.