Steak sarnie with onions and blue cheese

Method

1. Set a heavy-based frying pan over a high heat. Pat the steak dry with kitchen paper, then brush with a little oil and season with a pinch of salt. Cook the steak for 3-4 minutes on each side for medium (or less/more until cooked to your liking), then leave to rest in a warm place.
2. Add a splash of water to the pan, then scrape the bottom with a wooden spoon to lift any charred goodness (see Know-how). Turn the heat down to low medium, add the butter and, once melted, stir in the onion, thyme and a little salt. Cook, stirring regularly, for 10-15 minutes until softened and beginning to colour. Stir in the vinegar and sugar, then cook for 5 minutes more until reduced and sticky.
3. Meanwhile, mix the mayo, mustard and honey in a small bowl. Slice the rested steak into strips. Spread the toast with the mustard mayo, then top one slice with the leaves, steak and onions (discard the thyme). Crumble over the cheese, then top with the other slice and serve.