For the marinade, whisk vinegar, salt, pepper and honey. Add 4 tablespoons of oil drop by drop. Wash and clean the cucumber and cut into thin slices. Peel onion and cut into thin rings.
Wash the fish, pat dry, divide into 8 equal pieces and season with salt and pepper. Turn the fish in the flour. Heat 1 tablespoon of oil in a pan. Fry the fish on each side for about 2 minutes.
In the meantime rinse and drain the sprouts. Spread the cucumber slices evenly on 4 plates. Sprinkle with the marinade. Arrange onion rings, fish and sprouts on the plates and garnish with parsley.