For his foray into double-digits this year, Max wanted a birthday party at the Gravity Vault, a local rock-climbing gym. He also requested Evites “to save paper” (and himself from the embarrassment of a homemade invitation). For the first time, however, this budding Cake Boss wanted to collaborate on a cake, so we kept it simple with surprisingly good results.
We made three 9×12 cakes from boxed mixes (2 Funfetti and 1 chocolate), and stacked them into two three-layer cakes — the Funfetti one was wider because I cut each cake in half and had one half left over. The chocolate cake was cut into thirds and stacked into a narrow column. Made two or three batches of the usual marshmallow fluff buttercream frosting and tinted it tan with a little orange + a little brown gel food coloring, to stick the layers together. I trimmed both cakes a bit and saved some of the chocolate trimmings for the exciting intentional crumb coat step. (Note: if you are a skilled cake shaper, you might want to make this cake look a little less rectangular and more jagged and rock-wall-y, but I was afraid to try.)
So, usually when one frosts a cake, especially the non-smooth sides and underside, s/he starts with a crumb coat, a coating of frosting that catches the stray crumbs and eventually gets hidden under a second smooth, crumb-free topcoating of frosting. Normally, this is a PITA, but not in this case. Rocks (and artificial rock walls) have speckles. Time to embrace the crumb coat! In fact, amp it up by crumbling and mixing the leftover chocolate cake trimmings into the frosting. One warning, though: before adding extra crumbs to your frosting, save a cup or so of the original smooth frosting for writing. The crumby mixture gets stuck in a pastry bag tip and makes writing very challenging.
My son really enjoyed adding chocolate rocks to the sides of the cake. Encourage your helper to vary the size and colors of these rocks just like on climbing walls. Maybe one of you clever people can work out how to make climbing ropes out of thin licorice, but we ate our materials before we could come up with a more satisfying solution.