To use royal icing and ganache together to make a design, it is important to have both at a similar consistency before starting. As soon as the cake has been coated with the ganache icing, place the royal icing in a decorating cone (see “Making and Using a Decorating Cone”) and use it to make the following designs:
HERRINGBONE: Squeeze horizontal lines the size of spaghetti on the top of the cake, leaving a ½- to ¾-inch space between bands. The royal icing should sink into the ganache at this point. Immediately draw the point of a small knife, like a paring knife, down the center and perpendicular to the lines. As the knife tip passes through the two icings, it should draw the band of white down into a V-shaped design. Working quickly, repeat this at equal distances from both sides of the first line.