Beef Up!
    1. Spread mustard across one side of four slices of the bread and top with the corned beef.
    2. Add the cheese and onion and then cover them with the remaining slices.
    3. Head the butter in a pan and grill them until golden brown; three minutes on each side.
    4. Take them out of the pan and place on plates.
    5. Cut into triangles and serve.