1. Preheat your oven to 350°F (175°C).

2. In a bowl, combine flour and powdered sugar. Add cold cubed butter and use your fingers or a pastry cutter to blend until the mixture resembles coarse crumbs.

3. Mix in the egg yolk and, if needed, add cold water 1 teaspoon at a time until the dough comes together.

4. Press the dough evenly into a 9-inch tart pan with a removable bottom. Chill in the fridge for 15 minutes.

5. Bake the crust for 15–20 minutes or until lightly golden. Let it cool completely.

6. In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer.

7. Pour the hot cream over the chopped chocolate in a heatproof bowl. Let sit for 2 minutes, then stir until smooth and glossy.

8. Stir in the butter, vanilla extract, and salt until fully combined.

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

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

11. Remove from the fridge about 10 minutes before serving for the best texture.