For sauce reduction, lightly crush peppercorns with a knife. Peel and finely dice the onion. Crumble bay leaf. Wash and coarsely chop the parsley. Wash and drain tarragon, pluck leaves from the stalks and chop finely.
Bring vinegar to the boil with 4 tablespoons of water. Add the peppercorns, onion, bay leaf, parsley and half of the tarragon and bring to the boil. Reduce to 2 tablespoons over medium heat. Then pour through a sieve.
Cut broccoli into florets from the stalk and wash. Wash and clean the mangetouts. Peel, wash and slice the carrots. Wash and peel asparagus and cut off woody ends. For the asparagus, boil up about 2 litres of water in a wide pot.
Season to taste with salt and sugar. Wash the lemon hot, cut into slices and add to the water. Simmer asparagus in boiling water for 15-20 minutes. In a second pot, simmer carrots and broccoli for about 10 minutes. After 5 minutes, add mangetout.
Wash the chervil, shake dry and, except for something to garnish, pluck the leaves from the stems and chop them. For the sauce, whisk the reduction and egg yolks. Whisk egg yolk mixture over a hot water bath until thick and frothy.
Beat the butter little by little in small flakes with a whisk. Add chervil and the remaining finely chopped tarragon leaves and season the sauce with salt, pepper and lemon juice. Arrange vegetables and sauce on a plate and garnish with chervil.