Stir together flour, grated chocolate and salt. Cut in shortening with two knives or blend with pastry blender until mixture resembles coarse meal. Combine milk and vanilla; add gradually to dry mixture, tossing lightly with a fork. Form into ball.
Roll out on lightly floured pastry cloth to ⅛" thickness. Cut in circle 1½" larger than inverted 9" pie pan. Fit loo