01 - Combine flour, cocoa powder, powdered sugar, and salt in a bowl. Add cold butter and rub in with fingertips or pastry cutter until mixture resembles coarse crumbs.
02 - Add egg yolk and ice water, mixing gently until dough comes together. Shape into a disk, wrap, and refrigerate for 30 minutes.
03 - Roll dough on a lightly floured surface to fit a 9-inch tart pan. Press into pan, trim edges, and prick base with fork.
04 - Freeze crust for 10 minutes while preheating oven to 350°F. Line with parchment, add pie weights, and bake for 15 minutes. Remove weights and bake 10 more minutes until set. Cool completely.
05 - Heat cream in saucepan until just simmering. Pour over chopped chocolate in a bowl. Let sit 2 minutes, then stir until smooth. Add butter and vanilla, mixing until glossy.
06 - Pour ganache into cooled crust and smooth top. Refrigerate for 1 hour until set.
07 - Arrange raspberries on top. For glossy finish, warm raspberry jam and brush over berries. Dust with powdered sugar if desired.