Make sure the steak is thick enough to get a good colour on each side before the inside is overdone
- 6 x 120-150g sirloin or striploin, no rind
- 300g watercress
- 6 soft sourdough rolls
- For the balsamic mushrooms
- 8-12 large Portobello mushrooms
- 40g balsamic vinegar
- A drizzle of olive oil
- 80g butter, cubed
- 300ml white wine vinegar
- 100ml white wine
- 1 shallot
- 2 sprigs tarragon
- 2 egg yolks
- 30ml reduction, see recipe
- 300g clarified butter, at room temperature
- 1 tablespoon chopped tarragon
1 Coat the meat in sunflower, rapeseed or vegetable oil and season well with salt. Heat a cast-iron griddle pan until very hot. Cook the steak on a very high heat to your preferred doneness. We like medium rare. The exact timing depends on the thickness but we estimate about 2.5 minutes each side and then resting time.
2 Place mushrooms, gill-side up, on a roasting tray. Drizzle with olive oil and balsamic vinegar. Scatter cubes of butter on top. Season to taste. Cover with baking parchment and then tin foil. Roast for 45 minutes at 80°C.
3 Place all the ingredients for the vinegar reduction into a pot, add a splash of water and reduce by a quarter. Allow to cool. You will end up with more than you need for this recipe but it keeps well and can be used to make mayo or aioli.
4 To make the béarnaise, in a steel bowl over a gently simmering pot of water, whisk the yolks and reduction continuously until doubled in volume. Be careful not to allow it to get too hot and scramble. Take off heat occasionally to control the temperature. When doubled in volume, carefully, in a thin stream while constantly whisking, add the clarified butter. Add chopped tarragon and season with salt.
5 To assemble, split a sub roll, spread béarnaise on each side. Put watercress on the bottom. Slice the mushrooms and place on top. Slice the steak, place on top of the mushrooms and dollop some more of the béarnaise on top.
Tip: Our slow roast tomatoes are good with this too.
Photography Credit: Harry Weir, assisted by Brian Clarke