In a microwave-safe bowl or heavy saucepan, melt 1/2 cup semisweet chocolate chips and 1/4 teaspoon shortening; stir until smooth. Cut a small hole in the corner of a pastry or plastic bag; fill with melted chocolate. Pipe overlapping 1-in. hearts onto waxed paper. Repeat to make three more sets of overlapping hearts. Let dry before removing from the waxed paper. Store in an airtight container at room temperature. Use as a garnish for desserts.