Cook the gooseberries with sugar to taste. I don't think there is much point in suggesting quantities or amounts of sugar - it partly depends on the variety of gooseberry and on how ripe they are. I don't usually add any water - just put the washed, topped and tailed gooseberries in a heavy-bottomed pan, sprinkle over the sugar and cook on a very low heat until soft.
For the panna cotta you will need;
900ml double cream
18 heads of elderflower (they need to be fully in bloom and ideally picked on a sunny day)
6 table spoons caster sugar
3 leaves gelatine
Heat the cream very gently in a large saucepan with the elderflower heads stirred in (it smells gorgeous). When it has just come to the boil, take it off the heat and leave for at least half an hour to infuse. Stir in the sugar and heat to nearly boiling again and then sieve into a large jug. Meanwhile, soak the leaves of gelatine in cold water and when fully softened after about five minutes squeeze the water out of them and beat them into the warm cream in the jug. When they are fully dissolved pour the liquid into small moulds - ramekins are ideal - lined with cling film, cool, and then put into the fridge to set over night. Turn out the ramekins onto individual plates and serve with the stewed gooseberries.