Peel the potatoes and cook them in lightly salted water. Melt about 30g of butter in a pan and sauté the cooked potatoes in it.
Add the parsley, mix well and season with salt and pepper. Melt the remaining butter in a saucepan and stir in the flour with a whisk. Now add the milk and bring to a boil, stirring constantly.
Add the dill and immediately remove the sauce from the heat. Add lemon juice and season with salt and pepper. Heat some oil in a frying pan and fry the salmon fillet on both sides for about 3 minutes each until cooked. Season with salt and pepper and serve with the sauce and parsley potatoes.