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 hall.
Roll out on lightly floured pastry cloth to ⅛" thickness. Cut in circle 1 ½" larger than inverted 9" pie pan. Fit loosely in pan; pat out air bubbles; turn edge under and flute.
Sprinkle with chopped pecans and press gently into pastry. Prick sides and bottom with a fork.