Heat the vanilla custard gently in a heavy-bottomed saucepan over low heat.
Add the dark chocolate and stir until completely melted and smooth. Remove from the heat and allow the chocolate custard to cool completely.
Melt the butter in a frying pan over medium heat. Add the kataifi pastry and cook for 2–3 minutes, stirring frequently until golden and crisp. Transfer to a plate and let cool.
In a large mixing bowl, combine the pistachio cream, 250ml double cream, and 2 tablespoons icing sugar. Whip until soft peaks form.
Fold 75g of the toasted kataifi pastry into the pistachio mixture, reserving the remainder for garnish.
In a separate bowl, whip the remaining double cream with the remaining icing sugar until soft peaks form.
Assemble the Dubai Chocolate Trifle by spooning a layer of pistachio kataifi cream into the bottom of serving glasses.
Add a generous layer of crumbled brownies.
Spoon over the cooled chocolate custard.
Add another layer of the pistachio cream mixture without disturbing the custard.
Finish with whipped cream, the reserved toasted kataifi pastry, and finely chopped pistachios.
Serve immediately or chill for 20–30 minutes before serving.