Peel, wash and quarter the potatoes. Clean and wash the carrots and cut diagonally into slices.
Melt the butter or margarine in a saucepan, first sweat the potatoes in it, then add the carrot slices. Season with salt and pepper. Add the vegetable stock and cream. Cook on a mild heat for about 12-15 minutes.
In the meantime, clean and wash the spring onions and cut them diagonally into slices. Add to the carrots and potatoes and cook for about 5 minutes. Season to taste with salt and pepper. Sprinkle in the sauce thickener and bring to the boil briefly.
Wash the fish, cut it into bite-sized pieces and add. Let it steep for 5 minutes. Chop the dill and fold in carefully at the end.