Clean and wash broccoli and cut into florets. Cut broccoli stems into slices. Wash the plaice fillets, dab dry and cut them in half lengthwise. Sprinkle with 2 tablespoons of lemon juice.
Season with salt and pepper. Wash and pluck the herbs. Place fish fillets next to each other on the work surface and cover with herbs. Roll them up and fix them with wooden skewers. Cook broccoli in boiling salted water for about 12 minutes.
Bring 1/4 litre of water, 2 tablespoons of lemon juice, white wine, 1 teaspoon of salt, peppercorns and bay leaf to the boil. Cover the fish rolls and let them simmer at low heat for about 8 minutes. Stir sour cream and starch until smooth.
Wash the sprouts and drain well. Lift out fish rolls and keep warm. Sieve the fish stock and bring to the boil again. Stir in sour cream and simmer for about 3 minutes. Season sauce with horseradish, salt, pepper and sugar.
Drain the broccoli. Serve with fish rolls and some sauce. Sprinkle with sprouts. Add the rest of the sauce. Garnish with lemon, dill and parsley if desired.