Prepare the Crust Base

1. In a bowl, mix crushed biscuits, chopped pistachios, melted butter, and brown sugar until it resembles wet sand.
2. Press the mixture firmly into cylinder molds or small ring molds on a lined tray.
3. Chill in the refrigerator for 15-20 minutes to set.

Make the Blackberry Layer

1. In a saucepan over medium heat, combine blackberries, sugar, and lemon juice. Stir occasionally until berries soften.
2. Mix cornstarch with 1 tbsp of water, then stir into the berry mixture. Cook until thickened.
3. Let it cool slightly, then spread evenly over the chilled crust.

Create the Cheesecake Filling

1. In a large bowl, beat cream cheese until smooth and creamy.
2. Gradually add powdered sugar and vanilla extract, mixing until light and fluffy.
3. Gently fold in whipped heavy cream to keep it airy.
4. Spoon over the blackberry layer and smooth the surface.

Prepare the Pistachio Mousse

1. In a bowl, whisk together pistachio paste, powdered sugar, and whipped cream until fully combined and fluffy.
2. Spread this over the cheesecake layer as the final layer.

Chill Until Set

1. Sprinkle chopped pistachios around the edges for texture.
2. Cover and refrigerate for at least 4 hours (overnight is best for firm layers).

Garnish & Serve

1. Carefully unmold the towers.
2. Decorate with fresh blackberries, extra pistachios, and a dusting of powdered sugar.
3. Serve chilled and enjoy every creamy, nutty, and fruity bite.