My husband Michael, the engineer, is the designer for all our sons’ birthday cakes. He’s a big fan of Duff Goldman and watches Ace of Cakes often trying to pick up any tips he can. We only tackle cakes like this three times a year and we are definitely not pros. I bake the cakes and whip up the frosting and fondant and he does all the assembly and decorative work. Here’s our story on how we made the Lego Star Wars Stormtrooper birthday cake.
We always begin planning the birthday cakes months in advance because Michael likes to let the design percolate in his head for a while, so back in March we asked Top Gun what kind of cake he wanted for his next birthday, and for some reason he just couldn’t decide. He asked for a delta wing green airplane, Mater from the movie Cars, a dinosaur, Transformer (that would have been hard), and Yoda. He eventually settled on a dragon and we almost had it figured out, but then at the last minute he changed his mind and asked for a Lego Star Wars Stormtrooper cake. He was very specific and even picked out the stormtrooper model. We managed to dodge the Transformer cake for now, but Michael is pretty sure it’s in our future.
Because the heads on the Lego figures are a little oversized, Michael knew he would have to adjust for that by using something lightweight for the head, in this case rice crispies. As Michael took measurements on the figure and adjusted for scale, he realized he would have to make the legs and body a little wider to keep the cake vertical. As we stacked the cakes for the body it began to tip and we tried inserting a chopstick to stabilize it, but it wasn’t enough and we ended up using two half inch, 8-inch long dowel rods. Once the dowel rods were in the cake held up a little better, but it still leaned a bit.
Fortunately Top Gun didn’t care if the cake was leaning a bit or if the legs weren’t quite to scale, he was just one happy guy when he saw his birthday cake, and that’s good enough for us.
We do have some tips and thoughts to share on making the cake.
Below are the frosting quantities, which may vary slightly depending on how thick you apply it. You can make extra frosting and have leftovers for other uses, or you can start with the quantities listed and make more if needed. If you make two full batches of vanilla buttercream you should have just enough. We find using Wilton frosting gel colors help keep the colors consistent if you have to make another batch. Colors do tend to darken after resting a day.
- Bake the cakes up to one day before and allow them to cool completely. Freezing them for about 30 minutes before assembly makes them easier to carve, although on this project the cake carving is minimal.
- Make the frosting up to three days before. Cover the surface with plastic wrap and store in the refrigerator. Allow to come to room temperature before frosting the cake.
- Because the frosting is white, the chocolate cake tends to show through the crumb layer. We recommend letting the crumb layer dry completely (we dried it overnight) before adding the outer layer. You can also use a yellow cake if you prefer, because the crumbs won’t show up quite as much.
- Make the arms days in advance and compress the rice crispies until they are almost rock hard. Let them air dry overnight or over several nights without frosting. Even rice crispies have some weight to them particularly once you add the frosting and the arms were starting to fall off by the time we sang the birthday song. If we were to make something like this again, we would embed a wire skeleton in the arms, using the coated wires that keep toys connected to the packaging. Or if you don’t mind going inedible, Styrofoam would be an easy solution for the arms, (see the train birthday cakes). Green florist foam you can find in any craft store could also be used.
- Hang the arms and add the head at the very last minute so it all stays together.
- Use the chopsticks to hold the arms in place; one in the upper arm and one under the hand hooks.
- Because the head is top heavy, we recommend doing the finally assembly in place. Don’t try to put it all together in the kitchen then carry it half way across the house with candles lit, because you’re just asking for disaster.
Our Thoughts on Fondant
You can use fondant for the cake rather than buttercream, either purchased or homemade. Zoe of Zoe Bakes (one of my favorite bakers) has a tried and true recipe for homemade fondant or you can purchase premade fondant. Michaels craft stores now sell a Duff branded fondant that we’ve heard is pretty good, even edible, though it’s rather pricey. Fondant gives the cake a professional-looking, sleek, smooth surface, but no one in our family will eat it and that’s why we skip it. Wet paper towel can also be used to smooth out the final coat of buttercream, though it probably won’t be as smooth as rolled fondant.
LEGO STAR WARS STORMTROOPER BIRTHDAY CAKE
- Lego Star Wars stormtrooper toy or photo
- 2 (9×13) cake pans, greased with a layer of parchment in the bottom
- stand mixer with paddle attachment, or hand mixer and large bowl
- wax paper
- 3-quart bowl, coating with nonstick spray (for modeling the rice crispies)
- 2 (8-inch long) dowel rods, ½ inch diameter
- 2 chopsticks, cut in half
- 1 large pizza pan or serving platter
- 1 #3 piping tip + coupler
- 1 quart-sized freezer bag (for piping frosting)
- angled frosting spatula
- toothpicks (for portioning gel colors)
- FROSTING: Make both batches of the vanilla buttercream, set aside 1-½ cups, and tint it black. The color improves while sitting, so you can make this a day or two ahead of time. Refrigerate if making ahead.
- ARMS: Start by pressing rice crispies into three rectangles, about 3 in by 6 in by 2 in. Mini loaf pans are about the right size for this. Shape the two arms with your hands, compacting the rice crispies until they are almost rock hard. Set aside and allow to dry completely for a day a or two. Use the remaining rectangle for the helmet.
- HEAD: Press rice crispies into the greased bowl, compacting the rice crispies as much as possible, until it is completely full. Turn the molded shape out onto a nonstick surface. Use your hands to press and mold the crispies into the shape of the helmet, using a small knife to shave where necessary. Shape the remaining “arm” of rice crispies into the shape for the top of the helmet and press it into place. Take the shaved extra bits and form into a 4 in by 1 in tall “cookie” that represents the neck. Allow to dry completely for a day or two.
- CAKES: Cut one sheet cake into thirds (about 4 inches) widthwise. Cut two pieces from the other sheet cake, one 6 inches wide and one 4 inches wide (there will be about a 2 in strip leftover). Place the 6 inch piece on a small piece of wax paper on the serving platter/pizza pan, then add a layer of frosting. Stack the three equal pieces of cake on top, adding frosting between the layers, then finally top with the single 4-inch wide layer. The layers should line up along the back of the cake with the bottom layer protruding on one side to form the feet. Cut some of the cake away in the middle of the feet section to define the feet. Take the two half-inch 8-inch long dowel rods and press them down through the layers, one in each leg. This will help stabilize the structure. (The chopstick in the photo didn’t work and was replaced with the dowels.)
- Use a serrated knife to trim the cake edges to make them even, trim the sides a bit to shape the shoulders. Cut a notch through the front and back of the bottom two layers to define the legs. Use the angled spatula to apply a thin crumb layer of the white buttercream all over the cake, then allow it to set up, about 30 minutes or more, overnight is even better. Apply the final layer of white buttercream once the crumb layer is set. While the frosting is still wet, smooth it all over with a wet paper towel using a paper-mache technique and gently pulling, not sliding off, this will give you a more smooth, fondant-like finish. Allow the buttercream to set up, about 30 minutes. Pipe the black decorations on the chest and back.
- Apply the white buttercream on the arms, then coat the hands in black. While it’s still wet, smooth it all over with a wet paper towel similar to above, then allow the buttercream to set up, about 30 minutes.
- Apply the white buttercream all over the head, then smooth it all over with a wet paper towel and allow the buttercream to set up, about 30 minutes. Then pipe the black decorations on the helmet.
- Attach the arms using the chopsticks. Put one through the upper arm and one underneath the hand hook.
- Place the round rice crispy neck base on the stormtrooper shoulders, centering it. You may need to cut space for the dowels.
- Gently place the head on top of the cookie, balancing it in place. (We usually put a dab of frosting on something like this to hold it in place, but it didn’t work with the rice crispies.) You’re done!