4 x 200g fillet or porterhouse steak
8 x thick cut sourdough slices
1 onion, thinly sliced
1 cos lettuce
Swiss cheese, cut into thin slices
Grill bread smeared with butter.
Cook steak on a hot grill pan, on one side for a minute or so. Once you turn the beef fillet lay slices of cheese on top so it melts while cooking the other side of the steak.
Assemble sandwich, with mustard, mayo, lettuce, tomato, avocado and hold it together with a skewer of gherkins and pickled onions.