Preheat the oven to 180°C (350°F).
Prepare a baking dish by greasing it lightly.
In a large bowl, combine melted butter and kataifi pastry.
Add the sugar, vanilla extract, and a pinch of salt to the kataifi mixture.
Press half of the kataifi mixture into the prepared baking dish.
Melt the dark chocolate in a microwave or over a double boiler.
Spread the melted chocolate over the pressed kataifi layer.
Sprinkle the chopped pistachios over the melted chocolate.
Top with the remaining kataifi mixture, pressing gently.
Bake for 25–30 minutes or until golden brown.
Cool completely before slicing into bars.
