Wash the potatoes and cook with the skin in boiling water for about 20-25 minutes. Blanch the peas in boiling salted water for approx. 2 - 3 minutes, drain, rinse immediately with cold water and allow to drain. Wash the herring fillets and remove any remaining bones; Drain the mandarins while collecting the juice; Cut the onions into thin rings.
Mix the yogurt with 2 tablespoon mandarin juice, curry, a little salt and pepper. Mix with 2/3 of the mandarins, the cooled peas and the onion rings and season to taste.
Roughly chop the dill, peel the potatoes, melt the butter in a saucepan, add the dill and toss the potatoes in the dill butter.
Arrange the herring fillets and potatoes with a little sauce on the plates and sprinkle with the retained mandarins, garnish with dill if necessary. Serve the rest of the sauce separately.
Tip:
If possible, I use new potatoes for this dish, as they can be tossed in the butter with their skins and do not have to be peeled. The potato peels should then be brushed well before cooking, but in addition to being washed.