Preheat your oven to 350°F (175°C). In a mixing bowl, combine pistachio flour, sugar, and eggs until smooth. Melt butter and fold it into the mixture. Pour the batter into a greased 9-inch round cake pan and bake for 25-30 minutes or until a toothpick comes out clean. Let cool for 10 minutes before transferring to a wire rack.

Whip heavy cream in separate bowls until soft peaks form for both mousse layers. Melt white chocolate in 20-second intervals in a microwave. Fold melted chocolate into whipped cream. Blend raspberry puree with sugar and gelatin (or agar-agar) until smooth. Repeat for mango puree.

Place cooled pistachio cake on a serving platter. Spoon half of the white chocolate mousse over the cake, smoothing it into an even layer. Spread raspberry mousse on top, followed by mango mousse. Optionally, repeat layering once more and finish with mango mousse. Smooth the top and set aside.

Cover the assembled cake with plastic wrap and chill it for at least 6 hours, preferably overnight.

After chilling, remove from the refrigerator and let it sit at room temperature for 15 minutes before slicing. Garnish with fresh raspberries and mint leaves before serving.