Chocolate Butter Tarts

In large bowl, stir flour and cocoa with salt. With pastry blender or 2 knives, cut in butter and shortening until mixture resembles coarse crumbs with a few larger pieces. In liquid measure, whisk egg yolk with vinegar; add enough ice water to make 1/3 cup (75 mL).

Gradually sprinkle egg mixture over flour mixture, stirring briskly with fork until pastry holds together. Press into disc; wrap in plastic wrap. Refrigerate for at least 1 hour or until chilled or for up to 3 days.

Filling: In bowl, vigorously whisk together brown sugar, corn syrup, egg, butter, vanilla, vinegar and salt. Set aside.

On lightly floured surface, roll out dough to 1/8-inch (3 mm) thickness. Using 4-inch (10 cm) round cookie cutter (or empty 28 oz/796 mL can), cut out 12 circles, rerolling scraps once if necessary.

Fit circles into 2-3/4- x 1-1/4-inch (7 x 3 cm) muffin cups. Divide pecans and chocolate chunks among pastry shells. Spoon in filling until three-quarters full.

Bake in bottom third of 450˚F (230˚C) oven for about 12 minutes or until filling is puffed and bubbly and pastry is golden. Let stand on rack for 1 minute. Run metal spatula around tarts to loosen; carefully slide spatula under tarts and transfer to rack to let cool.