1.Brush the beef with oil and season well. Sear the steaks on both sides until medium rare or cooked to your liking, then rest before cutting. Prepare the salad ingredients.
2.For the sauce: simmer the vinegar, onion and rosemary until reduced to about 2 tablespoons. Strain off the liquid and place in a glass or stainless steel bowl with the egg yolks.
3.Whisk over a saucepan of boiling water until foamy and pale. Gradually add the butter while whisking until thick and creamy.
4.Slice the steaks into strips and place into rolls with the salad ingredients.
5.Drizzle over the sauce and season with cracked pepper and sea salt. Serve with fries and tomato sauce.
Change the salad ingredients to suit your taste or add a little cheddar cheese to the mix. If your sauce splits, never fear – whisking in a tablespoon or two of mayonnaise should bring it back.Note