Combine crushed biscuits and melted butter until evenly moistened. Press mixture into small cylindrical molds to form the base, then chill for 15 minutes.
In a large bowl, beat cream cheese, mascarpone, pistachio paste, sugar, vanilla, and lemon zest until smooth and creamy.
Spoon the pistachio cheesecake mixture evenly into the molds over the biscuit base. Smooth the tops and refrigerate for at least 3–4 hours, or until set.
Add blackberries, sugar, and lemon juice to a saucepan. Cook on low heat for 8–10 minutes until thickened, then cool completely.
Spread a thin, even layer of blackberry compote over each tower. Top with a swirl of mascarpone or pistachio mixture.
Add chopped pistachios, fresh blackberries, and edible flowers. Dust lightly with powdered sugar before serving.
