Preheat oven to 375 degrees F. Lightly grease 12 2-1/2-inch muffin cups; set aside. Prepare brownie mix according to package directions. Divide batter evenly among prepared muffin cups. Bake in preheated oven for 24 minutes. Cool in pan 10 minutes; loosen sides and remove from pans. Cool cupcakes completely on wire racks.
Using the handle of a wooden spoon, make a small hole in the side of each cupcake by twisting carefully. Turn cupcakes bottom sides up. Place a star stencil onto a cupcake and sprinkle with powdered sugar; lift stencil carefully. Repeat with remaining cupcakes.
Or, place candy coating, if using, in a small microwave-safe bowl. Heat on 50% power (medium) for 1 minute; stir until smooth. Cool about 5 minutes; spoon into a small, heavy plastic bag. Snip a small hole in one corner of the bag. Pipe swirls and other desired designs onto cupcakes. Sprinkle with sanding sugar, luster dust, and nonpareils, if desired, or dust with powdered sugar.
Place a little chocolate frosting on the end of a pirouette cookie. Gently push the frosted end of the pirouette into the hole in the side of a cupcake to make the handle of the fairy wand. Repeat with remaining frosting, cookies, and cupcakes. Makes 12.