1. COMBINE flour, 1/2 cup plus 1 tablespoon sugar, baking soda and salt in large bowl; cut in peanut butter and shortening, using pastry blender or 2 knives until mixture resembles coarse meal.
2. COMBINE milk, egg yolk and vanilla extract in small bowl; beat with fork until blended. Add to flour mixture. Transfer mixture to an electric mixer; beat at low speed until well blended. Divide dough in half. Wrap with plastic wrap. Refrigerate at least 1 hour.
3. HEAT oven to 350° F.
4. ROLL each half of dough between sheets of plastic wrap to 1/8-inch thickness. Cut with 2 1/2-inch heart-shaped cookie cutter. Place half the cut-outs 1 inch apart on ungreased baking sheets. Place about 1/2 measuring teaspoon jelly in center of each. Top with remaining cutouts. Press edges with fork. Pierce top several times with toothpick. Sprinkle tops of cookies lightly with sugar.
5. Bake 10 to 11 minutes or until golden brown. Sprinkle again with sugar. Cool 2 minutes on baking sheets; transfer to cooling racks to cool completely.