To make the chocolate pastry crust:

Cup of Yum
1. In a large bowl, combine the flour, powdered sugar, cocoa powder, and salt.
2. Add the diced butter and blend in using two forks, your fingers, or a dough blender until combined with a crumbly texture and no pieces are larger than the size of a pea.
3. Slowly add the cold water just until the dough comes together.
4. Form the dough into a flattened disc, wrap in plastic, and refrigerate for at least 30 minutes or up to 2 days.
5. Preheat oven to 350˚F (180˚C). Grease 12 tartlet pans with butter.
6. On a lightly floured surface, roll the refrigerated dough into an even, thin circle about 1/8 inch (3 millimeters) thick.
7. Cut out circles of dough using a cutter slightly larger than the width of the tartlet pans.
8. Press each circle into the prepared pan. Bring together the scraps of dough and roll out again, then cut if needed to make more circles.
9. Cover each circle of dough in the pan with parchment and add pie weights or uncooked rice. Bake in the preheated oven for 15 minutes.
10. Carefully remove the pie weights and parchment from the pan and continue to cook the crust for another 5 minutes. Remove from the oven and set aside.

To make the cheesecake filling:

1. Decrease oven temperature to 325˚F (163˚C).
2. In a large bowl, beat together the cream cheese and sugar until smooth and fluffy.
3. Beat in the egg, followed by the sour cream and salt. Scrape in the seeds from the vanilla bean and combine.
4. Pipe or spoon the cheesecake filling into the partially baked pastry crusts.
5. Bake in preheated oven just until set, 15-20 minute. Do not brown. Allow to cool in pan for 5 minutes, then carefully remove to a wire rack.
6. Once cooled to room temperature, transfer the tartlets to the refrigerator and chill thoroughly, 1 to 2 hours.

To make the Chocolate Ganache:

1. Pour the cream into a small saucepan over medium heat.
2. Right before coming to a boil, remove from heat and add chocolate pieces. Allow to sit for 30 seconds, then whisk until smooth.
3. Transfer the ganache to a small bowl, cover, and refrigerate, whisking occasionally, until firm enough to pipe.
4. Drizzle the ganache over chilled cheesecake tartlets or place in a piping back with a small tip and draw desired designs.