Ingredients: Sliced tomato, sliced onion, avocado, gerkins/pickles, cheese, whatever else you want in your sandwich, some sort of steak, sauce of your liking (I used HP sauce which no one seems to know about), some sort of bread (I used a focaccia like bread).
Method: Cook the onion with some sugar and salt until soft and caramalised. Meanwhile slice the tomato, gerkins. Set onion mix aside. Flatten steaks until they are about 1/4-1/3 bigger than your bread (as they will shrink when you cook them). Heat a grill pan till smoking hot and cook steaks for about 30 seconds a side. Slice avocado whilst steaks are cooking (have to bea ninja to do this). Place a slice of cheese ontop of the stead and rest the steaks. Place bread onto the pan. Lightly toast (keep you eyes on them because they burn quickly). Spread the sauce onto the bread. Top with everything and eat =]
Pretty simple and quick. Tastes awesome!