Roughly grate the peeled potatoes, squeeze out a little and mix with the egg, salt and pepper.
Heat a little oil in a non-stick pan. To portion the rösti, I put a large (approx. 8 cm) serving ring in the pan, add the appropriate amount of potato mixture and put the ring in the next place.
Fry the rösti on both sides for about 4 minutes.
In the meantime, cut the herring fillet into larger pieces, mix the cranberry jam with the mustard and cut thin onion rings.
Place the fillet pieces, onion rings and a generous dollop of jam on the finished hash browns.