Peel and wash the potatoes. Cut potatoes vertically close together, but do not cut through. Place in a large greased ovenproof dish or fat pan. Season and sprinkle with parmesan. Spread 30 g butter in flakes on top. Bake in a hot oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3) for about 25 minutes
Wash the salmon, pat dry and remove any bones. Wash lemon and lime, dab dry. Cut lime and 1/2 lemon into slices. Squeeze the remaining lemon. Sprinkle salmon with 1 tbsp. lemon juice. Season with salt and pepper. Place the citrus slices on the fish, tie them up with kitchen string if necessary
Push the potatoes to the edge of the mould. Place the salmon in the middle and bake for another 25-30 minutes
Peel and chop the onion. Fry in 30 g of hot butter. Add flour and sweat. Stir in stock and cream. Bring to the boil and simmer for about 5 minutes. Season to taste with salt, pepper, sugar and the rest of the lemon juice. First mix the egg yolks with some sauce, then stir carefully into the sauce (do not boil any more!)
Wash herbs. Chop half and stir into the sauce. Spread the remaining herbs on the salmon about 5 minutes before the end of the baking time. Arrange everything. Serve with a fresh green salad