Place a steamer basket in a wide pan, fill with water to just below the bottom of the basket. Add the vegetables, season with salt, cover and cook over a medium heat for approx. 15 mins. until just soft. Remove, mix with the oil and herbs.
Heat the oil in a pan. Sauté the shallot and garlic for approx. 3 mins. Pour in the vermouth and reduce almost completely. Add the sour single cream and water, bring to the boil, then simmer for approx. 5 mins. Add the lemon zest and juice, season. Blend the dressing ingredients, stir in the herbs.
Season the fish fillets, dust both sides with flour. Heat the clarified butter in a large, non-stick frying pan and fry the fish fillets in batches for approx. 2 mins. on each side, serve with the vegetables and lemon dressing.