Skirt steak has a deep, beefy taste that stands up well to fire. It’s long and flat, cooks quickly, and slices up beautifully against the grain. It doesn’t cost a fortune, but when treated right, it eats like a much fancier cut. I like to give it a short marinade just to soften it up and add a little background seasoning.
Marinate the Steak. Pat the steak dry with kitchen paper. In a shallow dish, mix the marinade ingredients. Add the steak and turn to coat well. Cover and refrigerate for at least 2 hours, or up to 4. Take it out 30 minutes before grilling to come up to room temperature.
Make the Butter. In a bowl, mix the softened butter, horseradish, chopped chives, salt, and pepper until smooth. Spoon onto clingfilm, roll into a log, and chill until firm.
Get the Grill Hot. Light your BBQ and set it up for direct heat. You want high heat for this—skirt steak likes a good sear. Brush the grill with a bit of oil to prevent sticking.
Grill the Steak. Place the steak over the hottest part of the grill. Cook for 3–4 minutes on each side, depending on thickness. You’re aiming for medium-rare to medium. If the ends are thinner, give them a little less time.
Rest and Serve. Transfer the steak to a board and rest it for 5–10 minutes under foil. Slice across the grain into thin strips. Top with slices of the horseradish butter just before serving.