Trace a star design several times on a piece of paper. Place paper on a baking sheet and cover with waxed paper. Microwave 1 bag (12 ounces) semisweet chocolate chips and 1 teaspoon shortening on high for 1 minute; stir. Microwave at additional 10- to 20- second intervals, stirring until smotth. Cut a small hole in the corner of a pastry or plastic bag. Attach a small round pastry tip with a coupler. Fill bag with melted chocolate. Following traced designs, pipe chocolate onto waxed paper. Chill until the chocolate is firm, about 15 minutes.
Carefully remove the stars with a metal spatula. Store in a cool, dry place in a covered container.