Method:
1 Heat oil in a frying pan over high heat, add steak and cook for 2 minutes on each side for rare, or until cooked to your liking. Remove to a plate, cover to keep warm.
2 Add a little more oil to the frying pan, add onion rings and cook over medium heat for 4-5 minutes or until onion softens and caramelizes a little.
3 Combine dijon mustard and mayonnaise in a small bowl.
4 Place 1 slice sourdough on serving plate, spread over mustard mayonnaise, top with cos, tomato, steak, onions and cheddar cheese. Season with salt and pepper, serve.
