1. Make the tart crust: In a food processor, pulse the flour, butter, 1/4 cup sugar, and salt until mixture resembles coarse meal. Add the egg and pulse just until dough begins to hold together. Form the dough into a disk, wrap in plastic, and refrigerate for at least 1 hour.

2. Preheat oven to 375°F. Roll out the dough on a lightly floured surface and press it into a 9-inch tart pan with a removable bottom. Trim the edges and prick the bottom with a fork. Bake for 20 minutes, then let cool completely.

3. Make the chocolate filling: In a medium saucepan, heat the cream over medium heat until just simmering. Remove from heat and add the chopped chocolate. Let sit for 2-3 minutes, then stir until the chocolate is completely melted and the mixture is smooth.

4. In a separate bowl, whisk the 2 eggs and 1/4 cup sugar together. Slowly pour the egg mixture into the chocolate mixture, whisking constantly.

5. Pour the chocolate filling into the prepared tart crust. Bake for 20-25 minutes, until the center is just set. Let cool completely.

6. Garnish the tart with gold leaf flakes just before serving.