01 - Preheat oven to 350°F (175°C).
02 - Combine flour, cocoa powder, granulated sugar, and salt in a mixing bowl.
03 - Add cold cubed butter and use a pastry cutter or food processor to blend until the mixture resembles coarse crumbs.
04 - Mix in egg yolk and 2 tablespoons cold water. Stir just until the dough begins to come together, adding remaining water as needed for consistency.
05 - Shape dough into a disk, wrap in plastic wrap, and refrigerate for 30 minutes.
06 - Roll dough on a lightly floured surface to fit a 9-inch tart pan. Press dough into pan, trim excess, and prick base with a fork.
07 - Line shell with parchment paper and fill with baking weights or dried beans. Bake for 15 minutes. Remove weights and paper, then bake an additional 10–12 minutes, until firm. Allow shell to cool completely in the pan.
08 - Heat heavy cream in a saucepan just below boiling point. Pour over chopped dark chocolate in a bowl; let stand for 1 minute, then add butter and stir until smooth and glossy.
09 - Pour ganache into the cooled tart shell and use a spatula to smooth the surface. Refrigerate for at least 1 hour, until ganache is set.
10 - Neatly arrange halved strawberries over the set ganache.
11 - If using, gently warm apricot jam and brush over strawberries for a shiny finish.
12 - Slice tart and serve chilled or at room temperature.