Mix all the sauce ingredients together with a good grind of pepper and a pinch of salt and set aside. Put a griddle pan over a high heat. Drizzle the cut side of the bread with 1 tbsp of the olive oil and griddle, pressing the top of the bread down, until the cut side is toasted and lightly charred in places. Remove from the griddle and rub the toasted side of the bread with the cut garlic. Spread the bottom slices of the bread generously with the sauce.

Keeping the griddle over a high heat, rub the sirloin steaks with the vinegar, then generously season with salt and pepper and drizzle with 1 tbsp of the oil. Get your extraction fan going or open the back door or window and griddle the steaks on high for 1-2 mins on each side for rare-medium or 3 mins on each side for cooked through. As soon as the steak is done to your liking, lift onto the sauced slice of bread to rest and allow the bread to soak up the juices.

Meanwhile, drizzle the onions with the rest of the oil, then griddle, pressing them down with a spatula for 3 mins on each side until charred. Lift them off and separate them into rings over the steaks, then crumble over the cheese, if using. Lay the tomato slices on top followed by the watercress or rocket, then finally the Little Gem leaves. Spread the top slices of bread with the rest of the sauce and close the sandwiches with them. Press down lightly, cut in half, if you like, and serve.