Brownie

1. Preheat oven to 180°C (360°F). Grease and line a 9 x 9 inch (23 x 23 cm) square pan with baking paper.
2. Melt the butter and semisweet chocolate together in a medium bowl, either over a hot water bath or in the microwave in short bursts. Set aside to cool slightly.
3. In a large bowl, whisk the eggs and caster sugar until smooth. Stir in the melted butter-chocolate mixture until just combined.
4. Using an electric beater, beat the mixture for several minutes until it’s pale, thick, and doubled in volume. This step is the secret to getting the shiny, crackly top.
5. Sift in the flour, cocoa powder, baking powder, and salt. Gently fold until just combined.
6. Fold through the walnuts (if using). Pour batter into the prepared pan and smooth the top.
7. Bake for 25–30 minutes. A toothpick inserted should come out with a few gooey crumbs. Let brownies cool completely in the pan.

Pistachio Layer

1. Tear the kataifi pastry into small strands. Toss with melted butter and spread onto a tray. Bake at 180°C (360°F) for 10–12 minutes, until golden and crisp. Cool completely.
2. Once cooled, break the pastry into small crunchy pieces. In a large bowl, mix these pieces directly into the pistachio spread until evenly coated.
3. Spread this pistachio-kataifi mixture evenly over the cooled brownie base, pressing down gently to create an even layer.

Chocolate Layer

1. Melt the dark or milk chocolate until smooth. Pour it over the pistachio layer and spread evenly with an offset spatula.
2. Let it set at room temperature or chill for 15–20 minutes until the chocolate is firm but not rock hard.
3. Drizzle extra pistachio spread on top for decoration.
4. Sprinkle lightly with flaky salt, cut into squares, and enjoy.