Spread some buttercream between the layers of the cake and place the cake in the fridge for 1 hour, or until firm. Carve a crater into the side of the cake with a serrated knife. Coat the cake in a thin layer of buttercream – don’t worry if crumbs show through, this “crumb coat” layer is meant to catch all of the crumbs. Return the cake to the fridge and chill for 30 minutes, or until the buttercream has stiffened.

Cover the cake in another layer of buttercream. To make the geode, fill the crater with rock candy, placing the darkest colour in the center and the lightest colour on the outside. The buttercream acts as a “glue” to stick the rock candy to the cake. Sprinkle edible glitter onto the rest of the cake and enjoy!