Line a large baking sheet with heavy foil; grease foil.
In a large microwave-safe bowl combine chocolate candy coating, milk chocolate, and shortening. Microwave, uncovered, on 100 percent power (high) for 11/2 to 2 minutes or until melted, stirring every 30 seconds.
Pour melted milk chocolate mixture onto prepared baking sheet. Spread to a circle about 1/4-inch thick.
In a separate microwave-safe bowl, microwave white baking chocolate for 30 to 60 seconds or until melted, stirring every 15 seconds. Transfer melted white chocolate to a piping bag fitted with a small open tip or a plastic bag; snip corner off. Pipe concentric circles over chocolate. Pull a toothpick or a bamboo skewer from center to outer edge, wiping toothpick between each pull. Top chocolate with gummy candy and licorice to make spiders.
Chill until firm, about 30 minutes. Use foil to lift from baking sheet. Serve whole and let your guests serve themselves, or break into pieces to serve. Refrigerate candy between layers of waxed paper in an airtight container for up to 2 weeks.