a kitchen paintbrush; a piping bag fitted with a large French decorating tip; a 2-inch round cookie cutter
Coat the outside of the sugar cone with an even layer of corn syrup using a kitchen paintbrush. Roll in the gold sanding sugar. Set aside to dry, about 20 minutes.
Meanwhile, examine the cake and designate which side will be the front. Place the white frosting in a piping bag fitted with a large French decorating tip. Pipe a large circle of frosting on the front top edge of the cake. Continue piping circles connecting the first circle to the top center of the cake, and then down the right side of the cake. Place the cone on the front top edge of the cake in the piped frosting circle. Arrange half a package of the candy ropes across the front of the cake to create fringe (or bangs), trimming with scissors if needed.
Twist half a package of the candy ropes and place them around the base of the horn. Continue to place groups of candy ropes around the horn and down the piped side of the cake, creating a mane. Braid a few candy ropes together and work them into the mane, if desired. Pipe four large swirls of frosting over the candy ropes, traveling from the horn to the top center of the cake; cover with the rainbow sprinkles.
Using a 2-inch round cookie cutter, gently score a half-circle in a dark chocolate melting wafer. Move the cutter back and forth until the wafer is cut into two pieces. Use a half-moon piece to create a winking eye to the left of the mane, pressing it into the frosting. Dot a tiny amount of frosting on the backs of the white confetti sprinkles and adhere them to the remaining dark chocolate melting wafer, arranging them parallel to each other. Place the wafer in the frosting to the right of the mane on the cake. Place the two pink candy melts on either side of the cake for blushing cheeks.
Snip the marshmallow in half diagonally with kitchen scissors. Immediately dip the sticky edges in the blue sanding sugar. Pipe two mounds of frosting on either side of the rainbow candy mane and stick the marshmallow pieces upright into the frosting mounds for two ears. Serve immediately.