Nutrition: Per serving
Combine the mayo, mustard, horseradish, half the lemon juice and some seasoning in a bowl. Peel the beetroot and thinly slice, then cut each slice into thin matchsticks and put in the bowl with the mayo dressing. Repeat with the celeriac, then fold the veg through the dressing. Chill for at least 30 mins. The veg will continue to soften the longer it’s left in the dressing. Will keep chilled for up to a day.
Remove the steaks from the fridge 30 mins before cooking. Rub each steak with a little oil and season well. Heat a frying or griddle pan over a high heat until very hot, then cook the steaks for 2-3 mins on each side for medium, or until cooked to your liking. Transfer to a plate to rest for a few minutes.
Meanwhile, split each ciabatta half and rub the cut sides with the cut sides of the garlic, then press the bread, cut side down, onto the hot pan and toast for 1-2 mins.
Toss the watercress or rocket with the remaining lemon juice. Trim away the fat from the steaks, if you like, then thinly slice. Lay the steak slices over the base of each ciabatta. Top with the remoulade and a handful of the dressed leaves. Drizzle any resting juices from the steak plate over the remaining ciabatta slices and sandwich these on top. Serve hot.
