Make crust: Stir together the flour, cocoa and salt in a large mixing bowl. Using a pastry blender or two knives, cut in shortening until mixture resembles coarse crumbs. With a fork, stir in water, 1 tablespoon at a time, until mixture begins to hold together and all the dough is moistened. Divide dough into sixths. Form each sixth into a ball. Cover with plastic wrap and refrigerate 30 minutes.

Remove one dough ball at a time and, on a lightly floured surface, roll into a 6-inch circle. Transfer to a 6-ounce ovenproof custard cup. Gently press into bottom and sides of cup. Trim edges. Repeat with remaining dough.

Heat oven to 400 degree F. Line each cup with foil and bake 8 minutes. Remove foil; bake 5 minutes more or until firm. Cool completely on a wire rack.

Make filling: Stir together sugar and cornstarch in a medium saucepan over medium heat. Add milk, chocolate and vanilla, and stir until thickened and bubbly. Cook and stir 2 minutes more. Remove from heat. Slowly stir 1 cup of the hot mixture into the beaten egg yolks. Lower heat, then carefully pour egg-yolk mixture into hot filling in pan. Bring just to boiling, stirring constantly, 2 minutes. Remove from heat. cover surface with plastic wrap and let cool 10 minutes.

Pour filling mixture into baked crusts. Cover and chill for 2 to 24 hours before serving. Top with whipped cream. Makes 6 cups.