Mix mustard, sugar, vinegar and oil. Wash the dill, chop finely except for a little bit and stir in. Wash fish, dab dry and cut into pieces. Pour into a shallow bowl, pour sauce over it. Peel onion, cut into thin rings and spread over it. Marinate for about 1 hour
Wash the chives and chop finely. Peel, wash and roughly grate the potatoes. Mix both with salt and pepper. Heat butter in a pan and bake about 20 cakes until golden brown. Keep warm
Arrange the cakes with mustard herring, gravad salmon, sour cream and prawns. Garnish with rest of dill
Drink: ice-cold vodka, for example from Absolut