Place the gelatine leaves in a bowl of cold water and allow to soften.
Split the vanilla pod in half and scrape out the seeds. Place the vanilla seeds in a pan with the cream, milk and chestnut puree. Warm through and then stir in the gelatine leaves. Once dissolved, pour the mixture into individual moulds and leave to set in the fridge.
Zest and juice the orange. Retain the orange zest to use for the biscuits. Add the juice and the Armagnac to the prunes. Leave to absorb.
Mix the orange zest, flour, sugar and butter together in the food processor until the mixture forms a ball. Remove and roll into a cylinder in cling film. Leave to firm up in the fridge. Once set, slice the biscuits and bake for 8 to 10 minutes at 180'c.
Serve the panna cottas topped with the boozy prunes and finish with the orange peel biscuits.
«To ensure that this dessert is thoroughly set, feel free to prepare it advance anc chill overnight.»