Clean the leek, wash it and cut it into rings. Blanch in boiling salted water for 4 minutes, drain well. Wash the fish fillet, sprinkle with lemon juice and salt. For the hollandaise, melt butter.
Beat the egg yolk and wine in a hot water bath until thick and frothy. Stir in butter drop by drop. Season to taste with salt and pepper. Fill leek into an ovenproof dish. Pour half of the hollandaise sauce over it.
Put the fish fillet on top. Add the rest of the hollandaise sauce. In the preheated oven (electric cooker: 175 °C/ gas: level 2) for about 30 minutes . Serve garnished with lemon wheels and dill.