5 kg minced beef, it needs to be the fatty mince not reduced or lean
2 sliced red onions
Handful of chopped flat-leaf parsley
2 tbsp oyster sauce
2 tbsp tomato ketchup
1 egg yolk
1 packet pre-sliced processed cheese like Kraft slices or Gouda works really well too
Knead all the ingredients together in a large bowl until they are very well combined. Shape into thin round patties and chill for a good hour. Trim your cheese so it’s slightly smaller than your burgers then place a slice on top of one burger and sandwich another burger on top, pinch the edges together well and really seal it up. Heat up a heavy frying pan then cook the burgers probably for about 5 minutes on each side until nice and brown. I would test run one first so that if your cheese starts to leak out you know to make the others with smaller pieces of cheese and sealed up better. You can also grill these burgers under a medium grill. Serve in a bun with all your favourite trimmings.