GREASE large baking sheet. Place on damp kitchen towel; this will help secure baking sheet when you knead fondant later.
COMBINE butter, corn syrup and 1 1/4 cups powdered sugar in large, heavy-duty saucepan. Bring just to a full boil, stirring constantly, over medium-low heat. Remove from heat. Add remaining 1 cup powdered sugar, peppermint extract and 3 to 4 drops of food coloring. Stir vigorously for 2 minutes or until well blended. Pour fondant onto prepared baking sheet; do not spread. Let stand for 4 to 5 minutes or until just cool enough to handle. Do not let fondant cool too much as you will not be able to knead. Lift up edges of fondant with rubber spatula and fold to center to make a mound. Knead for about 2 minutes or until soft. Flatten fondant to roughly a 6 x 4-inch rectangle and place on a piece of plastic wrap. Cover fondant with another piece of plastic wrap. Roll out to roughly 1/8-inch thickness to form a 12 x 8-inch rectangle. To make a more even rectangle, fondant can be trimmed to size. Keep fondant covered with plastic wrap so it will not dry out.
LINE another large baking sheet with wax paper. Melt morsels and vegetable shortening in uncovered, medium, microwave-safe bowl on HIGH (100%) power for 1 minute: STIR. Morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until morsels are smooth. Pour half of melted chocolate onto prepared baking sheet. Cover remaining melted chocolate with plastic wrap; set aside. Spread melted chocolate evenly with back of spoon or small metal spatula to roughly a 12 x 8-inch rectangle. Layer will be thin. Refrigerate for 3 minutes or until soft to the touch.
REMOVE top layer of plastic wrap from the fondant. Carefully invert fondant onto slightly chilled chocolate bottom layer. Press fondant lightly to adhere to bottom layer. Remove top sheet of plastic wrap. Spread remaining melted chocolate over fondant. Refrigerate for 15 to 20 minutes or until firm.
CUT out heart shapes with cookie cutter starting around edges. If candy gets too soft while cutting, refrigerate for a few minutes to firm up. Or, if candy is too cold to cut, allow to stand at room temperature to warm up slightly. Store refrigerated between sheets of wax paper until ready to serve.
NOTE: Candy can be cut out into small rectangles instead of hearts. Yield will be more.