For the pickled onions
1 1/4 cup white wine vinegar
½ cup castor sugar
2 red onions, finely sliced
For the chipotle yogurt
6oz 0% Greek yogurt
2oz chipotle chili paste or 2oz canned chipotles, drained and chopped
sea salt and freshly ground black pepper
For the fish
5oz plain white flour
5oz sparkling water
5 fl oz sunflower or vegetable oil
1 lb skinned white fish (eg cod or hake), cut into bite-size pieces
1/2 iceberg lettuce, shredded
8 small soft wheat tortillas
finely chopped coriander leaves
4 lime wedges
To make the pickled onions, place the vinegar and sugar in a small pan. Bring to the boil, then reduce the heat and simmer for a couple of minutes. Remove from the heat, add the finely sliced onions, and set aside to cool.
For the chipotle yogurt, stir together the yogurt and chipotle paste or chopped chipotle, then season to taste and set aside.
To make the batter for the fish, mix together the flour and sparkling water in a large shallow bowl. Heat the oil for a few minutes in a large sauté pan over a medium heat, being careful to not let it get too hot (you can test to see if it is hot enough by dropping in a piece of bread – it should sizzle). Quickly dip the fish in the batter to coat lightly and then fry in the oil, in batches if necessary, for a couple of minutes on each side. Remove with a slotted spoon and drain on kitchen paper.
To serve, place a little shredded lettuce in each tortilla, top with some fish, a dollop of chipotle yogurt and a spoonful of pickled onions, and fold in half to make a soft-shell taco. Serve with a scattering of coriander and a wedge of fresh lime on the side.
For a healthier option, simply cook the fish for 5 minutes on each side under a grill rather than battering and frying it.