Line an 8x8 inch square baking pan with parchment paper, leaving an overhang on two sides.

In a large mixing bowl, combine the crushed biscuits, cocoa powder, and 120g of melted butter. Stir until the mixture is uniform and resembles damp sand.

Press the biscuit mixture firmly and evenly into the bottom of the prepared pan. Place in the refrigerator to set while preparing the filling.

Melt 30g of butter in a large skillet over medium heat. Add the chopped kataifi pastry and toast, stirring constantly, for 5-8 minutes until golden brown and crispy.

Transfer the toasted kataifi to a medium bowl and allow to cool slightly. Add the pistachio cream and tahini, stirring until the kataifi is thoroughly coated.

Spread the pistachio-kataifi mixture evenly over the chilled biscuit base using an offset spatula.

In a heat-proof bowl, combine the milk chocolate, dark chocolate, and coconut oil. Melt using a double boiler or in the microwave in 30-second increments, stirring until smooth.

Pour the melted chocolate over the pistachio layer and spread to the edges. Sprinkle lightly with sea salt flakes.

Refrigerate the pan for at least 2 hours, or until the chocolate and filling are completely firm.

Lift the brownies out of the pan using the parchment overhang and slice into 16 squares using a sharp knife dipped in hot water.