1. In a food processor, combine the flour, butter, and 1/4 cup sugar. Pulse until the mixture resembles coarse crumbs.

2. Add the egg yolk and water, and pulse until the dough just begins to come together.

3. Shape the dough into a disc, wrap in plastic, and refrigerate for at least 1 hour.

4. Preheat the oven to 375°F (190°C).

5. On a lightly floured surface, roll out the dough to fit a 9-inch tart pan with a removable bottom. Gently press the dough into the pan and trim the excess.

6. Bake the tart shell for 15-20 minutes, or until lightly golden. Allow to cool completely.

7. In a medium saucepan, heat the cream over medium heat until just simmering. Remove from heat and stir in the chopped dark chocolate until smooth and combined.

8. In a separate bowl, whisk together the eggs, 1/4 cup sugar, and salt. Slowly pour the egg mixture into the chocolate mixture, whisking constantly.

9. Pour the chocolate filling into the prepared tart shell and bake for 25-30 minutes, or until the center is just set.

10. Allow the tart to cool completely, then carefully remove the outer ring.

11. Gently apply the edible gold leaf sheets to the top of the tart, using a soft brush to help adhere the leaves.

12. Serve the dark chocolate tart with gold leaf at room temperature or chilled.