Wash the fish, dab dry, cut into cubes and chill. Clean, wash and slice the spring onions. Peppers clean, wash and dice. Wash cucumber and slice lengthwise into thin strips.
Mix with 1/2 teaspoon salt and set aside. Wash the potatoes and cook in salted water for about 20 minutes. Drain, rinse and peel. In the meantime, chop the fish cubes in portions in a lightning chipper.
Mix fish, half of the vegetables, 20 g flour and egg. Season to taste with salt, pepper and lemon juice and chill again. Melt the fat in a saucepan. Stir in 30 g flour and sauté briefly. Add milk while stirring, bring to the boil and simmer at low heat for about 5 minutes.
Stir in mustard and season with salt, pepper and nutmeg. Add the potatoes and warm up in the sauce. Wash the dill, dab dry and chop. Mix vinegar, sugar, dill, salt and pepper. Add 4 tablespoons of oil drop by drop.
Drain cucumbers and mix with vinaigrette. Form 8 small meatballs from the fish mixture. Heat 2 tablespoons of oil in a pan and fry the meatballs for 2 minutes on each side. At the end of the cooking time, add the remaining vegetables and let them fry.
Serve the meatballs with vegetables, potatoes and cucumber salad.