This chocolate-lined crust has been subtly—and seasonally—spiced to complement our Pumpkin-Chocolate Tart's rich filling.
In the bowl of an electric mixer fitted with the paddle attachment, combine flour, sugar, cocoa, salt, cinnamon, and cloves. Add butter; mix on low speed until butter is the size of small peas, about 5 minutes. Add egg; mix until ingredients come together to form a dough.
Preheat oven to 350 degrees. On a lightly floured work surface, roll out dough to just thicker than 1/8 inch. Brush off excess flour; transfer dough to a 10-inch tart pan with a removable bottom. Press dough into bottom and up sides of pan; trim excess flush with edge. Lightly prick bottom of dough all over with a fork. Chill until firm, about 30 minutes.
Bake shell until firm, about 15 minutes. Immediately sprinkle chocolate over bottom of shell; smooth with a spatula.