In a mixing bowl, combine cake mix, water, egg, and oil. Mix well. Place batter into a gallon-size resealable bag. Snip the tip and pipe the batter into the prepared pans until they are about half full. 

Bake for 10-12 minutes or until golden brown and cooked through. Remove from pan. Let cool for 2 minutes and invert pan onto a cooling rack. Let cool completely. 

Once donuts are cool, add butter, milk, and sugar in a bowl and whisk well. Dunk donuts into glaze and let excess drip. Place on a cooling rack and let remaining glaze drip off. Let set to dry. 

Divide frosting into fourths. Leave one-fourth of the frosting white. Tint remaining frosting with food coloring and pipe into separate piping bags with a star tip. 

Cut candy melts in half with a knife. 

To make horns, unwrap 4 candies and place them onto a microwave-safe plate. Microwave for 10 seconds. Roll the candy into a 6" long "snake" shape. Fold in half and twist. Shape the end to a point. Let cool and harden on wax paper. 

Once donuts are dipped in glaze and it's dry, use white frosting to attach the horn and ears to the donut. Use the colored icing to pipe a mane onto the unicorn. Add sprinkles and let set to dry. 

Makes 30 donuts.