In a medium bowl cream together sugar, butter and vanilla then add egg and combine.
In a medium bowl whisk together flour, salt, baking powder and cocoa, add dry ingredients to creamed mixture with a fork. Move to a lightly floured flat surface and knead gently until you have a soft dough (you may need to add a little more flour, but add a little at a time). Wrap in plastic and refrigerate for approximately 30 minutes.
Pre-heat oven to 350°. Grease and flour an 8 inch pie plate.
Remove dough from the fridge and roll to approximately 1/8 inch thickness (you will have extra dough, perfect for cookies) place in prepared pie plate, prick the bottom a few times with a fork. Cover with parchment paper and add dried beans or pie weights on top, bake for approximately 20 minutes (if pie is not baked, then bake for an additional 5 minutes without the beans). Remove from the oven, remove paper and beans, let cool.
While Crust is cooling make the filling. Heat the cream until hot but do not boil, add the chocolate and butter, whisk until smooth. (If chocolate does not completely melt, then pour mixture in a heat proof bowl and place over a small pot with water (make sure water does not touch the bottom of the dish), heat on low, stirring until mixture is melted and smooth. Let cool slightly.
Pour mixture over cooled crust, cover with plastic wrap and refrigerate for approximately 1-2 hours. Enjoy.
**With the extra dough I made cut out cookies and when they were cool I covered them with the extra chocolate filling.