Hull and chop fruit, then tip them into a bowl with the sugar and lemon juice. Bring a kettle of hot water to the boil and pour over 300ml boiling water. Leave everything to macerate until cool, then blitz in a food processor until smooth. Push the purée through a sieve.
Clear a shelf in the freezer and place a sided metal tray in to chill. Pour the mix into the tray and cover with cling film. Freeze the liquid until frozen around the edges and slushy in the middle. Use a fork to break up the ice into smaller crystals. Return the tray to the freezer. Repeat the breaking up process every half hour (at least three times) until it’s completely frozen and the texture of snow. For a quicker method: freeze the mixture in an ice tray, then blitz the cubes in a food processor just before serving. The texture will be slightly slushier, but just as delicious.