Prepare the Cake Base: Combine the ground biscuits, ground pistachio, and melted butter in a mixing bowl until crumbly. Press this mixture evenly into the bottom of an 18cm round cake pan. Preheat your oven to 180°C (350°F) and bake the crust for about 12.5 minutes until lightly golden. Allow to cool completely.

Make Raspberry Bavarois: Soak the gelatin leaves in cold water for about 5 minutes. Heat the milk with half of the caster sugar over low heat. In a separate bowl, whisk the remaining sugar with egg yolks until pale. Gradually pour the hot milk into the yolks, stirring constantly, then return it to the pan until it thickens. Off heat, add gelatin and raspberry puree, mixing well, and fold in whipped cream.

Create Pistachio Mousse: Heat the milk with pistachio paste until just simmering. In a bowl, whisk egg yolks and sugar until thick and pale, then mix with hot milk. Return to the saucepan until thickened. Stir in bloomed gelatin, then fold in whipped cream. Pour the mousse over the raspberry bavarois and smooth the top.

Serve: After chilling overnight, remove from mold. Sprinkle ground pistachios and garnish with fresh raspberries. Slice and serve cold.