“`html

1. Start by washing the raspberries thoroughly under cold water. Drain them and set aside.
2. In a medium saucepan, combine the raspberries, granulated sugar, and lemon juice. Cook over medium heat, stirring gently until the raspberries break down and the mixture becomes syrupy, about 5-7 minutes.
3. Once the raspberry mixture is ready, remove it from the heat and let it cool slightly.
4. In a small bowl, sprinkle the gelatin over the cold water and let it sit for about 5 minutes to bloom.
5. After the gelatin has bloomed, heat it in the microwave for about 10-15 seconds until it dissolves completely. Stir this into the warm raspberry mixture until well combined.
6. Allow the raspberry mixture to cool to room temperature while you whip the cream.
7. In a large mixing bowl, whip the heavy cream until soft peaks form. Be careful not to overwhip it; you want it to be light and fluffy.
8. Gently fold the cooled raspberry mixture into the whipped cream until fully incorporated. Be careful to maintain the lightness of the mousse.
9. Preheat your oven to 350°F (175°C). Grease and line an 8-inch round cake pan with parchment paper.
10. In a medium bowl, combine the finely ground pistachios, all-purpose flour, baking powder, and salt. Whisk together until well mixed.
11. In a large mixing bowl, cream the softened butter and granulated sugar together until light and fluffy, about 3-4 minutes.
12. Add the eggs one at a time, mixing well after each addition. Then stir in the vanilla extract.
13. Gradually add the dry ingredients to the wet mixture, mixing until just combined. Be careful not to overmix; a few lumps are okay.
14. Pour the batter into the prepared cake pan and smooth the top with a spatula.
15. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
16. Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes. Then, transfer it to a wire rack to cool completely.
17. Once the pistachio cake has cooled completely, use a serrated knife to slice it in half horizontally, creating two layers.
18. Place one layer of the pistachio cake on a serving plate or cake stand. This will be the base for your mousse.
19. Spread half of the raspberry mousse evenly over the first layer of cake. Use a spatula to smooth it out.
20. Carefully place the second layer of pistachio cake on top of the mousse layer.
21. Spread the remaining raspberry mousse over the second layer of cake, smoothing it out evenly.
22. In a separate bowl, whip the heavy cream with powdered sugar until soft peaks form. Spread this whipped cream topping over the raspberry mousse layer.
23. Garnish with chopped pistachios and additional fresh raspberries for a beautiful presentation.
24. Chill the assembled cake in the refrigerator for at least 2 hours before serving to allow the mousse to set.

“`