Raspberry Sorbet

Put the caster sugar, the water and the fine salt into a small pan.

Warm over medium heat for 3-4 minutes, stirring, until the sugar has completely dissolved and the syrup is clear.

Take it off the heat and cool it to room temperature, about 30 minutes.

Blitz the raspberries to a puree in a blender or with a stick blender.

Push the puree through a fine sieve into a bowl with the back of a ladle, scraping the underside of the mesh as you go.

Stop when only dry pips are left in the sieve. It should give about 500g of puree.

Stir the cooled syrup and the lemon juice into the puree.

Do not cut the sugar back. It is not only sweetness: dissolved sugar lowers the freezing point, and it is the only thing standing between this and a solid block of ice. A little under a quarter of the finished weight is the working figure for a sorbet.

Chill the mixture in the fridge for at least an hour, until it is properly cold. A warm mixture spends its first hour in the freezer melting the ice around it and refreezes as coarse crystals.

Taste it cold and add a little more lemon juice if it tastes flat, remembering that cold mutes both sweetness and acid.

Churn it in an ice cream machine for 20-30 minutes, until it holds the mark of a spoon, if you have one.

Without a machine, pour the mixture into a wide shallow container so it freezes in a thin layer, and put it in the freezer.

Beat it hard with a fork every 45 minutes for the first 3 to 4 hours, working the frozen edges into the softer middle each time.

Do not skip a beating. The whole difference between sorbet and a block of ice is crystal size, and breaking the crystals up as they form is the only thing doing that job without a machine.

Freeze for a further hour, until it is firm enough to scoop but still gives under the spoon.

Move it to the fridge for 10-15 minutes before serving if it has been in the freezer overnight.

Eat it within a week. It keeps for a month but coarsens as it sits, and it is best in the first few days.