Blitz the frozen raspberries with the prosecco until it is completely smooth.
Push the pureé through a sieve to get rid of any pulp.
Put the cream and the sugar into a saucepan, heat over a medium heat until the sugar has dissolved. The increase the heat and boil rapidly for 2-3 minutes, stirring constantly.
Take the cream off the heat and add the raspberry + prosecco pureé. Then add the juice of one lemon, stir well and leave it to cool in the pan for about 15 minutes.
Divide the mixture between glasses or ramekins, then place into the fridge to chill for at least 4 hours.
To serve, sprinkle the freeze dried raspberries over the top. Garnish with the fresh raspberries.
This goes well with shortbread. For these I bought some lavender flavoured, heart shaped shortbread from Waitrose.