Heat a cast-iron griddle pan until searing hot. Add the steak and cook for about 5 minutes each side or until rare. Set aside for at least 15 minutes to rest or up to an hour is fine, then cut into thin slices, trimming down as necessary.
Place the potatoes in a pan of cold salted water and bring to the boil. Simmer for 15-20 minutes or until tender, then drain. Cook the eggs in a pan of simmering water for 7 minutes until soft-boiled. Drain and fresh under cold running water, then shell.
Meanwhile, make the dressing, place the vinegar, mustard, honey and seasoning in a screw-topped jar and shake until the salt has dissolved. Add the oil and shake again vigorously until you have a nice thick emulsion. Add the shallots, chives, parsley, gherkins and capers, shaking gently to combine.
While the potatoes are still warm, cut them into slices and arrange half in the bottom of a serving dish. Spoon over some of the dressing and then cover with a layer of the slices of beef. Repeat the layers, spooning a little dressing over each one. Cover with clingfilm and set aside at room temperature for an hour to allow the flavours to combine.
Just before serving, cut the soft-boiled eggs into quarters and arrange around the edge of the salad with the tomatoes. Garnish with parsley and serve straight to the table with a separate bowl of green salad and some crusty French bread.