How to make
Cut the leeks into round slices and braise them in 1 tablespoon of the butter. Smear an oven dish with the remaining butter and put the slices of leeks on the bottom.
Put the fish fillets onto a wooden board with the skins facing down. Sprinkle with salt and black pepper and then with finely chopped dill.
Roll up the fillets and put them on top of the leeks. Heat the oven to 520°F (270°C).
Prepare a sauce by mixing the mustard, vinegar, oil and sugar. Pour it over the fish and sprinkle with breadcrumbs. Bake for 25 min.
