Begin by mixing the ground biscuits and ground pistachios in a large bowl. Melt the unsalted butter and combine it with the dry ingredients until the mixture resembles wet sand. Press this mixture evenly into the bottom of an 18cm round pan. Bake in a preheated oven at 180°C for approximately 12.5 minutes or until slightly golden. Allow it to cool completely before adding the next layer.

In a small bowl, bloom the gelatin leaves in cold water for about 5 minutes. While they soften, heat the milk with half of the caster sugar in a saucepan over medium heat. In a separate bowl, whisk together the remaining sugar with the egg yolks until pale. Temper the egg yolks by gradually adding the hot milk, then return the mixture to low heat until it thickens to 82°C. Stir in the bloomed gelatin and warm raspberry puree, then let it cool slightly.

While the raspberry mixture cools, whip the cream with 10g of sugar until soft peaks form. Gently fold the whipped cream into the cooled raspberry mixture, ensuring not to deflate it. Once combined, pour the raspberry bavarois over the cooled cake base and spread it into an even layer. Refrigerate the cake for at least 4 hours or until set.

In a saucepan, heat the milk with the pistachio paste until just simmering. Meanwhile, whisk the egg yolks and sugar together in a separate bowl until light and fluffy. Gradually temper the yolk mixture with the hot milk, then transfer it back to the saucepan and cook until it thickens to 82°C. Remove from heat and fold in the bloomed gelatin when the mixture cools slightly.

Whip the additional cream until soft peaks form, and gently fold this into the cooled pistachio mixture to maintain its airy texture. Ensure everything is well blended but still light and fluffy. Pour the pistachio mousse over the set raspberry bavarois layer, smoothing the top with a spatula. Refrigerate the entire cake overnight to allow both layers to meld beautifully.

Once the mousse is fully set, remove the cake from the refrigerator, and carefully release it from the pan. Sprinkle the top with ground pistachios for added crunch and garnish with fresh raspberries for a pop of color. Slice the Raspberry Pistachio Mousse Cake into wedges and serve chilled.