Cover the potatoes with salted water, bring to the boil and cook covered over medium heat for 20 minutes. In the meantime, finely chop the dill and mix with the crème fraîche and mustard. Season with salt and pepper.
Grease two small casserole dishes (approx. 18 cm) with 1 teaspoon of butter each. Drain the potatoes and let them cool down briefly. Then cut into 1/2 cm thick slices. Layer the potato slices in the pan and spread a total of 1 tablespoon of butter in flakes over them.
Wash the salmon fillets and pat dry with kitchen paper. Then salt and pepper all around. Place 1 salmon fillet on each of the potato slices and brush with the dill cream. Cook the salmon in a hot oven at 200 ° C top / bottom heat (convection: 180 ° C) for about 20 minutes.