Bring water and sugar to a boil and cool.
Cut the herring fillets in pieces and onion in thin slices.
Layer the herring and onion in a glass with the soused herring spices.
Pour over the vinegar brine and cover with a lid.
The herring should be kept in the refrigerator for 24 hours before eaten.
Tip: Fresh dill gives this recipe an extra nice touch.
Many of our recipes of pickled herring is based on pre-pickled herring that can be bought in a selection of stores. Here is the recipe you should start with if you're making it from scratch.