- Boil a kettle of water and put it into a vacuum flask.
- Bring a pan of vinegar to the boil and keep it hot.
- Skin and fillet the fish; chop it up into 25 mm (1 in) cubes.
- Fry these in olive oil and when they’re just cooked, put the chunks into clean jars.
- Add ½ tsp pickling spice to each jar.
- Pour over equal parts of boiling water and vinegar. Tap the jar to get rid of trapped air.
- Cover with a layer of cling film (to prevent the vinegar from attacking the metal cap) and then screw on the caps.
- Add sliced onion, diced garlic, capers or chilli peppers instead of or as well as the pickling spice. Dried onion and garlic are useful here.
- Use appropriate herbs, such as tarragon, dill (weed) or thyme.