Peel the potatoes, wash them thoroughly and cook in boiling salted water for about 20 minutes. In the meantime, wash the fish, pat dry, sprinkle with 2 tablespoons of lemon juice and cut into 8 small slices.
Season with salt and pepper. Place the fish on a baking tray lined with baking paper. Bake in a preheated oven (electric cooker: 200 °C/ gas: level 3) for about 8 minutes. In the meantime, wash the dill, dab dry and cut into fine pieces.
Drain the fat in a saucepan, dust with flour, sauté and gradually deglaze with stock and milk, stirring constantly. Bring to the boil, season to taste with salt, pepper, sugar and the remaining lemon juice.
Whisk the egg yolks with a fork. Remove the sauce from the heat and stir in the egg yolks drop by drop. Arrange potatoes, fish and sauce sprinkled with pepper and dill. Garnish as desired with lemon slices and lemon balm.
A green salad tastes good with it.