Step 1

in a food processor, place flour, chopped cold butter, and vanilla sugar, and process to get fine crumbs. Gradually add chilled water and continue to mix until the pastry dough forms. Shape into a disk, wrap in a plastic film and refrigerate for 20 minutes.

Step 2

Grease a 9 inch/23 cm fluted tart pan with removable bottom. Using a rolling pin, roll out the pastry between two sheets of parchment paper until about 0.1 inch/3 mm thick. Line the tart pan with the dough and refrigerate for 15 minutes.

Step 3

Preheat oven to 355 F/180 C. Trim edges of the pastry with a knife and prick the crust (bottom and sides) with a fork before baking. Bake the tart crust for 20 minutes, until lightly golden. Let the crust cool down in the pan.

Step 4

Keep the oven temperature at 355 F/180 C. To make the chocolate ganache, process dark chocolate in a food processor for a few seconds or chop the chocolate into small pieces, and place in a bowl. In a saucepan, bring milk, heavy cream, and butter to a boil. Pour the milk mixture over the chocolate and gently combine with a hand whisk until homogeneous. Work with the whisk delicately in order not to produce bubbles in the preparation. Add eggs one by one to the chocolate mixture, stir until thoroughly blended.

Step 5

Pour the preparation into the cooled tart crust and bake for 15 minutes. The center of the tart will be wobbly.

Step 6

Let the tart rest for about 2 to 3 hours until the chocolate ganache is set. Then decorate the tart as you desire or leave it plain.