“This is a very grown-up, cleansing end to a meal, and easy too,” says food writer Diana Henry.

“With granitas there’s no mucking about with custards or ice-cream machines, just sweet liquid, a freezer and a fork. Pile the bittersweet crystals into chilled glasses and leave it at that.

“If you’re feeling particularly lazy, use a bottle of freshly squeezed juice.”

Ruby grapefruit and Campari granita

Ingredients:(Serves 4-6)

500ml freshly squeezed ruby grapefruit juice150g caster sugar5tbsp Campari

Method:

1. Gently heat the juice with the caster sugar in a saucepan until the sugar has dissolved. Leave to cool. Add the Campari, then pour the liquid into a wide, shallow freezable container and put it into the freezer.

2. After about an hour, fork the crystals forming round the edges into the rest of the juice. Keep doing this at intervals, forking the slush to break it up as it freezes. You want to end up with fine, glassy shards of ice.

3. If the mixture sets hard, just leave it out of the freezer for five minutes and fork it again before serving.

Crazy Water, Pickled Lemons by Diana Henry is published by Aster, priced £26. Photography by Jason Lowe. Available now