Put the gooseberries in a pan with the sugar and a couple of tablespoons of water and cook on a low heat, stirring every so often, until they begin to soften. Turn up the heat and continue cooking for 10-12 minutes until they have broken down to a jam-like consistency. Leave to cool.
For the jelly, bring the water and cordial to the boil, add the sugar and stir until dissolved then remove from the heat. Soak the gelatine leaves in cold water for a minute or so until soft. Squeeze out the water, add to the syrup and stir until dissolved, then leave the jelly to cool but do not let it set.
Break the sponge into pieces and put into a glass and pour over the Sauternes. Spread about two thirds of the cooked gooseberries over the soaked sponge. Then pour over the cooled, but not set, jelly so it just covers the sponge and gooseberry. Put it in the fridge for an hour or so to set.
Make the custard. Split the vanilla pod in half lengthways and scrape out the seeds with the point of a knife. Put the single cream, vanilla pod and seeds into a small saucepan and bring to the boil. Remove from the heat and leave to infuse for about 10 minutes.
In a bowl, mix the egg yolks, sugar and cornflour together. Take out the vanilla pod and pour the cream on to the egg mixture and mix well with a whisk. Return to the pan and cook gently over a low heat for a few minutes, stirring constantly with a wooden spoon until the custard thickens. Make sure it doesn't boil.
Remove the custard from the heat and give it a final mix with a whisk. Transfer to a bowl, lay a sheet of Clingfilm over the surface of the custard to prevent it forming a skin and leave to cool for about 30 minutes.
Once the jelly has set, spoon over the custard and leave to set for half an hour or so.
Now prepare the topping. Put the double cream, sugar, elderflower, lemon juice into a bowl and whisk till firm.
To serve, spoon the cream mixture on top of the trifle and top with gooseberry’s and dusted chocolate.