InstructionsReset

1. For the Crust: Adjust oven rack to middle position and preheat oven to 350ºF (175ºC). In a large bowl, whisk flour, cocoa powder, sugar, and salt together. Pour butter and water into the flour mixture and, using a flexible spatula, stir until well combined and a uniform dough forms.
2. Using your hands, pinch off and distribute 3/4 of dough over bottom of a 9-inch tart pan with a removable bottom. Press dough to an even thickness in the bottom of the pan. Pinch the remaining dough into smaller pieces and scatter evenly around the edge of the pan, then press dough into fluted sides of the pan. Press dough to even thickness until sides are completely covered.
3. Place the lined tart pan on a wire rack set in a rimmed baking sheet and bake until fragrant and firm to touch, 25 to 35 minutes, rotating pan halfway through baking. Set aside until ready to fill.
4. For the Filling: In a 12-inch skillet, melt 4 tablespoons butter over medium heat until foamy. Add kataifi pastry and cook, stirring often and breaking up clumps with a wooden spoon until browned, about 4 to 5 minutes. Transfer to a large bowl and let rest at room temperature until cooled, about 15 minutes.
5. Meanwhile, place pistachios on a 9- by 13-inch rimmed baking sheet and bake, stirring halfway through, until lightly browned and fragrant, 8 to 10 minutes. Add toasted pistachios to kataifi bowl along with pistachio cream, tahini, and salt. Using a flexible spatula, gently fold to combine. Transfer mixture into prepared chocolate tart crust, and, using an offset or flexible spatula, spread into an even layer; set aside.
6. Place chocolate in a medium heatproof bowl. In a small saucepan, combine heavy cream, corn syrup, and remaining 1 tablespoon butter to a simmer over medium heat, about 4 minutes. Pour over chocolate and let stand until chocolate softens, 1 minute, and stir until smooth. Cool chocolate mixture until warm but still pourable (100 to 105ºF or 38 to 40ºC), about 3 minutes.
7. Pour chocolate mixture over pistachio layer, and using an offset or flexible spatula, spread into an even layer. Refrigerate, uncovered, until ganache is set, about 1 hour. Garnish with chopped pistachios and flaky sea salt.