01 - Set oven to 350°F and grease a 9-inch tart pan with a removable bottom.
02 - Whisk together flour, cocoa powder, powdered sugar, and salt in a mixing bowl.
03 - Cut cold butter into dry mixture using a pastry blender or fingers until coarse crumbs form. Add egg yolk and 2 tablespoons ice water, mixing until dough just forms, adding more water as needed.
04 - Press dough evenly into tart pan, prick base with a fork, and freeze for 10 minutes.
05 - Bake crust for 15 minutes then remove and allow to cool completely.
06 - Heat heavy cream, milk, and butter over medium heat until simmering. Remove from heat, add chopped chocolate, and let stand for 2 minutes before stirring until smooth.
07 - Whisk in sugar, vanilla, salt, and eggs until mixture is glossy and fully combined.
08 - Pour filling into cooled crust and bake at 350°F for 15 to 18 minutes until edges are set but center remains slightly wobbly.
09 - Cool on a wire rack, then refrigerate for at least 1 hour until firm.
10 - Arrange fresh raspberries on top and dust with powdered sugar if desired before serving.