Make the sorbet syrup. In a small bowl, stir the sugar and stabiliser powder together thoroughly. Put the water and the glucose or runny honey in a saucepan. Heat gently to bring just to the boil.
Pour the contents of the bowl into the saucepan in a steady stream, stirring all the while with a whisk. Bring back to just boiling, then remove from the heat. Leave the syrup to cool until tepid before using. (It will keep for up to a week in the fridge.)
To make the raspberry gelato, blend together the raspberries, sugar and sorbet syrup.
Strain all or part of the mixture through a sieve into a bowl to remove the seeds – strain most of it, to leave a few seeds to remind me of the raw fruit, but not so many as to annoy. Transfer the mixture to your ice-cream machine and churn until fully firm.
Before serving, put the raspberry gelato in the freezer for half an hour or so to firm up. If it has been stored in the freezer longer and is too firm, allow it to soften in the fridge until scoopable.