Pickled fish

1. Carefully slice the onions for the pickling sauce into 5mm-thick rings. You don’t want the onions to be so thin that they cook away.

2. Mix the sauce ingredients in a large pan. Add the onions and cook gently until soft but not mushy (about 10 minutes). You can thicken the sauce with a teaspoon of cornflour mixed with a little cold water; add it to the sauce for the last 2 or 3 minutes of the cooking time.