1 tbsp of Lightly Seasoned vinegar blend (reserved from the pickling)
1⁄2 banana shallot, finely diced
1 tbsp of capers, roughly chopped
1 handful of mixed chopped herbs (preferably parsley, dill and tarragon)
Fresh lemon juice, to taste
Finely slice the celeriac and pumpkin into matchsticks and place in a bowl. Submerge in the quick-pickling vinegar and leave to pickle for 15 minutes.
Drain the pickled vegetables, reserving 1 tbsp of the pickling vinegar.
Make a quick rémoulade dressing by whisking together the oil, mustard and reserved vinegar. Stir through the shallots, capers and herbs, then fold through the drained celeriac and pumpkin. Season with salt, pepper and a squeeze of lemon juice.
Pat the steaks dry and season with salt and pepper. Cook in a smoking hot pan with a splash of oil for around 3–4 minutes on each side.
Allow the steaks to rest for 5 minutes before carving into 5mm slices, making sure you cut across the grain of the meat to avoid chewiness.
To assemble the sandwiches, butter the toast and add a handful of watercress to half of the slices. Top with the sliced steak, add plenty of rémoulade and close the sandwich. Serve immediately.