For the carpaccio, peel and halve the onion. Clean the beetroot. Bring vinegar, 3 l water, bay leaf, sugar, salt and beetroot to the boil. Cover and cook for about 20 minutes. Let the beetroot cool down in the stock and then peel it.
(Attention! They stain strongly, please wear disposable gloves.) Pre-cooked beetroots should only be drained and dabbed dry well.
For the truffle dressing, mix icing sugar and lime juice. Stir both oils vigorously. Stir in truffle paste. Slice the parmesan into shavings. Clean and wash the frisée, shake dry and pluck smaller.
Slice the beetroots into very thin slices and spread them on four plates like roof tiles. Sprinkle with the truffle dressing. Sprinkle with parmesan and frisée. Serve with baguette.