01 - Set the oven to 350°F.
02 - Combine flour, cocoa powder, powdered sugar, and salt in a bowl. Cut in cold, cubed butter until mixture resembles coarse crumbs.
03 - Incorporate egg yolk and ice water until dough forms. Shape into a disk, wrap in plastic wrap, and refrigerate for 30 minutes.
04 - On a lightly floured surface, roll dough and press into a 9-inch tart pan. Trim excess edges.
05 - Prick tart base with a fork. Line with parchment and fill with pie weights. Bake for 15 minutes, remove weights, bake an additional 5 minutes. Cool completely.
06 - Heat heavy cream to a simmer, pour over chopped chocolate and let stand for 2 minutes. Stir until smooth, then incorporate butter until ganache is glossy.
07 - Pour ganache into cooled crust and smooth the surface. Refrigerate for at least 1 hour until set.
08 - Arrange fresh raspberries over ganache. Optionally, brush with warmed raspberry jam for a glossy finish.
09 - Cut tart into servings and serve chilled or at room temperature.