Lightly spray 28 (1¼ x1-in.) molds in flexible plastic ice cube trays with nonstick spray; set aside.

Microwave baking chips in a medium microwave-safe bowl on HIGH at 15-second intervals until melted, stirring each time. Spoon chocolate into a disposable pastry bag. Cut off ¼-in. tip on end of pastry bag.

Pipe chocolate into prepared molds of ice cube trays, filling just until bottom of each mold is lightly coated with chocolate. Immediately press 3 marshmallows slightly into each section of chocolate. Drizzle with remaining melted chocolate.

Firmly tap filled ice cube trays on work surface a few times to compact ingredients. Garnish with cranberries and pistachios. Freeze for 10 minutes or until chocolate is set. Let stand at room temperature for 5 minutes. Pop chocolates out of ice cube trays before serving. If necessary, use the tip of paring knife to release. Store in covered container in refrigerator up to 1 week. Serve at room temperature.