Peel and wash the potatoes. Cook in salted water for about 20 minutes. Clean and wash broccoli and cut into florets. Steam them in approx. 100 ml covered water for approx. 5 minutes
Clean and wash the spring onion and cut into fine rings. Clean, wash and halve the tomatoes
Remove broccoli from the vegetable water and set aside. Pour milk into the vegetable water and bring to the boil. Add sauce thickener and bring to the boil again. Stir in mustard and season to taste
Wash the fish, pat dry and cut in half lengthwise once. Sprinkle with lemon juice, salt. Roll up the fish and pin it. Cover the rolls in the sauce and let them simmer at low heat for 5-6 minutes
Add spring onion and tomatoes and cook briefly. Heat broccoli in it. Serve everything. Add boiled potatoes