Clean, wash and cut the Romanesco and cauliflower into florets. Clean and peel the carrots, peel, quarter and slice the kohlrabi. Steam carrots and cauliflower in the broth in a large pot with lid for about 15 minutes until al dente. Steam Romanesco and kohlrabi for 8-10 minutes. In the meantime, rinse fish and pat dry.
Heat 2 tablespoons of oil in a frying pan and fry the fish for 8-10 minutes while turning. Peel the shallot and dice very finely. Drain the vegetables, collecting 200 ml of broth. Sauté shallot in remaining hot oil, add stock, milk and wine and bring to the boil. Add lemon juice and zest, season with salt and pepper. Bind with sauce thickener. Melt butter and toss vegetables in it. Season vegetables and salmon with salt and pepper. Wash the chervil, dab dry, pluck off the stems.
Bind with sauce thickener. Melt butter and toss vegetables in it. Season vegetables and salmon with salt and pepper. Wash the chervil, dab dry, pluck off the stems. Arrange vegetables with salmon fillet and sauce, garnish with chervil. Croquettes taste good with it