Clean the lamb`s lettuce (i.e. sort out bad leaves and remove the root ends) and wash in standing water.
Peel the celeriac and cut into large pieces. Sauté in lightly salted water with 1 tablespoon of vinegar (celery well covered) until soft. Took me about 25 minutes, then pour it over a sieve and let it cool down. Now either puree with a fork (this was done in the past) or with a hand blender.
For the dressing, mix well the remaining vinegar, salt and pepper, sugar, shallot, pureed celery and chives. Finally add the oil and mix everything well again.
Arrange the lamb`s lettuce loosely on a plate and drizzle with the dressing.
I decorate with 1 hard-boiled egg or a pretty flower for the sake of appearance.