Tip the onions, parsley, ketchup, oyster sauce and egg yolk into a large bowl with the mince.Use a large spoon or your hands to mix and knead everything together until completely combined.
Seperate the mix into six and roll into large balls.
Flatten the burgers slightly, place them in the fridge and leave to chill for at least 1 hour.
Cook either on a good hot BBQ or under the grill until cooked through.
Serve on burger buns with iceberg lettuce, mayonaise sliced tomoato and ketchup!