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Recipe 02

Flank Steak Sandwiches with Pickled Red Onions & Brown Butter Mayo

Yield
6-8
Time
1 hour, plus optional marinating

Complete recipe

Read from start to finish.

Before you start

Ingredients

Steak

  • 1.6 kg flank steak
  • 24 g kosher salt, about 1.5% of the steak weight
  • 2 tbsp olive oil
  • 2 tbsp Worcestershire sauce
  • 1 tbsp Dijon mustard
  • 3 garlic cloves, grated or minced
  • 2 tsp smoked paprika
  • 1 tsp black pepper
  • Optional: 1 tsp ancho chilli powder or chipotle powder

Quick pickled red onions

  • 2 large red onions, thinly sliced
  • 240 ml apple cider vinegar or white wine vinegar
  • 240 ml hot water
  • 2 tbsp sugar or honey
  • 2 tsp salt

Brown butter horseradish mayo

  • 120 g mayonnaise
  • 30 g butter
  • 1-2 tbsp prepared horseradish
  • 1 tbsp Dijon mustard
  • 1 small garlic clove, grated
  • 1 tsp lemon juice
  • Pinch of salt
  • Black pepper

Sandwiches

  • 6-8 ciabatta rolls, baguette sections, or sturdy sandwich rolls
  • 200-300 g provolone, Gruyère, fontina, raclette, or another good melting cheese
  • 2-3 handfuls arugula/rocket
  • Pickled red onions
  • Optional: crispy shallots
  • Optional: butter or olive oil for toasting the bread

Recipe notes

Notes

  • The steak should be sliced thinly and across the grain. Non-negotiable.
  • The cheese should be melted onto the bread, not onto the steak in the oven.
  • The brown butter mayo is the “wow” factor: rich, nutty, sharp, and just obnoxious enough.
  • Arugula adds peppery freshness so the whole thing does not collapse into pure meat-and-fat theatre.
  • Crispy shallots are optional, but very good.

9 steps

Method

Step 1 of 9

  1. Pickle the onions
    Put the sliced red onions in a bowl or jar. Mix the vinegar, hot water, sugar, and salt until dissolved. Pour over the onions and leave for at least 30 minutes. Longer is better.

Step 2 of 9

  1. Prepare the flank steak
    Find the direction of the grain before cooking. This matters. You will slice across it later.
    Cut the 1.6 kg flank steak into 3-4 large pan-sized pieces, not thin strips.

Step 3 of 9

  1. Season the steak
    Mix olive oil, Worcestershire sauce, Dijon, garlic, smoked paprika, black pepper, and optional chilli powder. Rub all over the steak pieces. Salt evenly with the 24 g kosher salt.
    Rest for at least 45 minutes, or refrigerate overnight uncovered or loosely covered.

Step 4 of 9

  1. Make the brown butter mayo
    Melt the butter in a small pan over medium heat. Keep cooking until it foams, smells nutty, and turns golden brown. Do not wander off; butter burns with enthusiasm.
    Let it cool for a few minutes, then mix with mayonnaise, horseradish, Dijon, garlic, lemon juice, salt, and black pepper. Taste and adjust with more horseradish or lemon if needed.

Step 5 of 9

  1. Cook the steak
    Heat a cast iron pan, grill, or plancha until very hot. Sear the steak pieces hard, about 3-5 minutes per side depending on thickness.
    Aim for:
    • Medium-rare: 52-54°C before resting
    • Medium: 56-58°C before resting

Step 6 of 9

  1. Rest and slice
    Rest the steak for 10-15 minutes. Slice very thinly against the grain. This is the difference between a steak sandwich and a jaw workout.

Step 7 of 9

  1. Toast the bread
    Split the rolls and toast them cut-side down in a pan with a little butter or olive oil, or under the oven grill/broiler.

Step 8 of 9

  1. Melt the cheese without overcooking the steak
    Put cheese on the cut side of the bread, then melt it separately:

    • Best: under the oven grill/broiler for 30-90 seconds.
    • Alternative: in a hot pan with a lid and a tiny splash of water beside the bread to steam-melt the cheese.

    Do not put the steak back in the oven.

Step 9 of 9

  1. Assemble
    Spread brown butter horseradish mayo on the bread. Add melted cheese, sliced flank steak, pickled red onions, arugula, and optional crispy shallots. Close the sandwich and press lightly.

Recipe preview

9 steps

A few ingredients

  • 1.6 kg flank steak
  • 24 g kosher salt, about 1.5% of the steak weight
  • 2 tbsp olive oil
  • 2 tbsp Worcestershire sauce
  • 1 tbsp Dijon mustard

The opening moves

  1. 01

    Pickle the onions Put the sliced red onions in a bowl or jar. Mix the vinegar, hot water, sugar, and salt unt...

  2. 02

    Prepare the flank steak Find the direction of the grain before cooking. This matters. You will slice across i...

  3. 03

    Season the steak Mix olive oil, Worcestershire sauce, Dijon, garlic, smoked paprika, black pepper, and option...

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