Sweet tart pastry.
Whisk together yolk, cream and vanilla in a small bowl.
Combine flour, cocoa, sugar and salt.
Rub in butter.
Add cream mixture untill dough forms. Make into 6" disk and refridgerate for 1hr up to 48 hrs.
Bake 30 mins at 375 deg F plus five mins without foil. Cool for thirty mins.

Filling.
Cream and milk at med/low until just starts to simmer. Stir in chocolate, sugar and salt and let stand for 5 mins.
Whisk eggs until blended. Stir in and whisk until blended.
325 deg F 15-20 mins in the cooled shell. If bubbles or cracks on surface pull out. Cool before cutting - serve warm.