Preheat your oven to 350°F (175°C).

Whisk together the all-purpose flour, cocoa powder, powdered sugar, and salt in a mixing bowl.

Mix in the cold, cubed butter until the mixture resembles coarse crumbs.

Add the egg yolk and gradually incorporate ice water until the dough comes together.

Press the dough into a tart pan with a removable bottom and chill in the refrigerator for 30 minutes.

Bake the tart crust in your preheated oven for 15-20 minutes, then let it cool completely.

Heat the heavy cream in a saucepan over medium heat until it begins to simmer.

Remove from heat and add the chopped chocolate. Stir until smooth, blending in the butter and vanilla extract if using.

Pour the ganache into the cooled tart crust and smooth the top with a spatula.

Refrigerate the tart for at least 2 hours or until the ganache is set.

Arrange fresh raspberries on top of the tart.

Dust with powdered sugar and garnish with mint leaves if desired.