Pre-heat the oven to 200°C or Gas mark 6.
Peel and finely chop the onion. Peel and crush the garlic.
Chop the parsley. Slice the tomato.
Crack the egg into a small mixing bowl and beat with a fork.
Place the mince, onion, garlic, parsley, mustard and egg in a large bowl and mix.
Using your hands, divide the mince into 4 equal portions.
Form into even size patties. Remember to wash your hands thoroughly after handling raw meat.
Heat the oil in a frying pan and cook the burgers for 5 – 10 minutes on each side until cooked through. Check that the burgers are thoroughly cooked and there are no pink juices.
Remove the burgers from the frying pan and place on an oven tray.
Slice the cheese. Top the burgers with a slice of tomato, blue cheese and onion marmalade.
Place the burgers into the oven and cook for 5 minutes until the cheese begins to melt.
Remove the burgers from the oven.
Serve in a toasted burger bun with a little rocket.