Prepare the Phyllo Dough: Gently fold the phyllo dough into squares or strips and arrange them in a 9x12 baking dish. Tuck the edges in neatly. Brush the melted butter evenly over the phyllo dough.
Bake the Phyllo Dough: Bake in a preheated oven at 350°F (175°C) for about 15 minutes, or until the phyllo is golden brown.
Make the Filling: In a saucepan over low heat, combine the condensed milk, pistachio butter, vanilla extract, tahini, and salt. Stir continuously until the mixture is smooth and well combined.
Assemble the Cake: Pour the smooth filling over the hot, baked phyllo dough. Spread it evenly and let it sit at room temperature until it cools and sets.
Decorate: Once the cake has cooled, drizzle melted dark chocolate on top, and sprinkle with chopped pistachios and a dusting of icing sugar.
Chill (Optional): For the best results, refrigerate the cake for a few hours before serving. It can be made in advance and stored in the fridge.
