Crew's Cake - Spiral Cake Tutorial

UPDATE: I received a nice email this morning from a reader in Malaysia (Hi, Deepa!) asking for more advice/help on how to carve the spiral. Unfortunately when I made this cake I didn't take any pictures of the carving process, darn! So, I took my little circles diagram below and made some notations on it about how we went about carving the spiral and I emailed that image back to Deepa. Meanwhile I thought I'd include it on this original post too in case anybody else might benefit from it. Happy cake-making!

My extended family got together for my nephew's 2nd birthday this weekend. My sister asked if I would like to make the cake instead of buying present, and of course I said yes! The theme was Cars (the movie) so I looked online for some ideas. When I found pictures of a Cars-themed spiral cake (like this, but much bigger and fancier) I knew I had to give it a try! As always, this cake took quite a while but I did as much ahead of time as I could: baked the cakes and froze them, and made & colored fondant and buttercream to help the decorating go faster the day of the party. The decorating was a lot of fun! Above you can see that my fondant mountains got saggy after it had sat for a while; most likely because each cake layer underneath was split into 3 layers with pudding in between. Everything was edible except for the three cars, and the sign on top. The blue sky is buttercream, along with the cacti, clouds, & piping detail. The road, road strips, Route 66 sign, rocks, mountains, and traffic light are fondant. Everyone loved the rocks; they were the easiest thing to make! I had made gray and tan fondant; to make each rock I just took a little bit each of gray & tan, and smushed/rolled them together and into a rock shape, and gave each rock a little texture from a frosting tip, a knife, or whatever was handy.

To figure out ahead of time how to successfully make the spiral while cutting off (wasting) as little cake as possible, Aaron & I stacked up the 3 cake pans I used: a 10", 8", and 6" round. We figured out that by stacking the cakes as shown below, the shape lent itself to a natural spiral. So, looking at my lovely diagram below, you can compare to the pictures above and see that the start of the road, where the Route 66 sign is, is just barely to the left of the bottom of the circles.
I used one cake mix for the 10" and split a second cake mix between the 8" & 6". I froze them overnight. The next morning I let them thaw a little and then assembled them: leveled the tops, split each cake into 3 layers, "dammed" the edges of each with a piping of thick frosting & filled layers with pudding, opted to do each cake upsidedown for the nice straight edges, stacked them all as shown in the diagram above, and returned the whole thing to the freezer for a couple hours to firm up before carving.

If you click to enlarge the diagram below it may help with carving your spiral cake. You can see how we stacked the 3 cakes, and the arrows show the way the road curved around all the way up to the top! Next time I'll take pictures of the carving process!

Aaron, who is much more artistic than I and a capable sculptor (he does all the cake carving for me when there is a need!), carved the spiral road. I covered the whole cake in chocolate frosting (it was a Boston Cream; our family's favorite) and returned it to the freezer again to firm up so the chocolate would be ready to take on the exterior buttercream & fondant.

The hardest part was making the road; I did it in 3 sections. I rolled out the black fondant and cut the inside curve with a pizza wheel, then laid it on the road and trimmed off the outside of the curve. That was the best way I could figure how to do it.

It was a really fun cake to do; it's always time-consuming but I really do enjoy it!