Spread frosting over cookie crust. Top with gumdrops. Melt white baking chips and 1 teaspoon shortening in small microwavable bowl uncovered on Medium-High (70%) 1 minute; stir. Continue to microwave 10 seconds at a time, stirring after each time, until chips can be stirred smooth. Drizzle over cookie. Let stand 15 to 20 minutes or until topping is set. To serve, cut into wedges.