Place the raspberries, caster sugar and freshly squeezed
grapefruit juice into a small saucepan set over a medium/low heat. Cook for 4 to 5 minutes, until the raspberries have broken down. Remove from the heat and divide the compote between six martini glasses or champagne flutes.Set aside and allow to cool.
Soak the gelatine in a bowl of cold water for 5 minutes, making sure the leaves are fully immersed.
Put the caster sugar, cream and grapefruit zest into a small saucepan. Cut the vanilla pod in half lengthways and scrape the seeds into the pan. Bring slowly to the boil, then take the pan off the heat.
Remove the gelatine from the water and gently squeeze
it with your hands to remove the excess water. Whisk the gelatine into the warm cream until it has broken down fully and is completely incorporated into the cream. Allow to chill slightly in the fridge.
When dividing the pannacotta between the glasses, pour the unset mixture over the back of a teaspoon to ensure the raspberry compote is not disturbed in the glass. Transfer to the fridge to set for 5 to 6 hours or overnight.