White, marinated fish which is slightly acidic is often served in Spain and Portugal. This Norwegian version is just as good. Frozen sprats can often be purchased and they are just as tasty as fresh ones.
Fillet the sprats to remove the backbone and guts, although the fillets should remain in one piece.
Place the fillets in a dish and pour over the vinegar to cover them. Cover and leave to stand in the fridge for an hour or overnight.
Pour off any excess vinegar, sprinkle with a bit of vinegar and serve, either alone or with a green salad, bread and some good oil. When preserved in vinegar the sprats will keep for a week in the fridge.