Method

• 1.
  Rub oil over steaks and set aside for 30 minutes to come to room temperature.
• 2.
  Meanwhile, for bearnaise mayonnaise, place the herbs and 100ml oil in a narrow jug. Blend with a stick blender until smooth (add a little more oil to loosen if needed).
• 3.
  Add mustard, vinegar, egg and a large pinch of sea salt. Blend, slowly adding the remaining oil, until smooth. Cover surface with plastic wrap and chill until needed. (Bearnaise mayonnaise will keep in an airtight container in the refrigerator for up to 3 days.)

• 4.
  Heat a large heavy-based frypan or barbecue to high heat. Season steaks, then sear the fatty edge of each steak for 2 minutes or until beginning to render.
• 5.
  Turn steaks flat and cook on one side for 4 minutes, then turn and cook for a further 2-3 minutes for medium-rare or until cooked to your liking.
• 6.
  Set aside to rest, loosely covered with foil, for 5-10 minutes. Slice steaks against the grain into 1cm slices.
• 7.
  Divide steaks among serving plates and serve with lettuce, French fries and bearnaise mayonnaise.