This is a 40" tall flaming chocolate wedding cake for 300 people that I created for my wedding in April 2015.
Step 1: Figure Out the Design
For the design of our wedding cake, I wanted to create something wild and unique, something with an interesting shape. In thinking about what I wanted it to look like, I got inspiration from Dr Seussian castles and structures, with their weird twisting shapes and improbable structural integrity. And because I met the girl I was marrying creating big fire art, it just had to be on fire! I knew early on that I would integrate a CNC cut metal structure to enable the cake to defy normal cake physics.
I started creating some 3d CAD designs. It took about 3 iterations before settling on a design, but I got one I liked. I was able to easily get the total volume of the shape from the CAD program, and that is what I used to size the cake. A healthy sized portion of cake is 10 cubic inches of volume, and we had 300 people, so I tweaked the design until it came out at about 3000 cubic inches.
Step 2: Do R&D
I had never made a cake this big before, and my previous cakes had tasted good but never came even close to looking pretty. Also, quantities and techniques really had to be nailed down before scaling up to the real thing. Finally, the cake design had lots of cantilevered angles, so I had to make some mockups to see what would actually hold up, and adjust the support structure design accordingly.
I had 3 cake R&D parties over several months. I would invite friends over- somewhat to help cook, but mostly to help eat!
Step 3: R&D Lab 1!
The first R&D lab was all about trying recipes. I tried 2 cake recipes, 3 fondant recipes, numerous filling recipes, a few icing recipes, and a ganache recipe. We tried them all- some were delicious, some were just weird and disastrous.
Pause for pastry glossary:
Fondant is that almost too-perfect looking outer layer of decoration seen on many wedding cakes. You roll it out with a rolling pin and then place it over the cake, and can also cut designs out of it, make shapes with it, and do all kinds of cool things that you see on pro cakes.
Ganache is a mixture of melted chocolate and heavy cream. It's viscosity goes from pretty liquidey when warm to quite solid when cool. It's the 'glue' used to hold the cake together, and the outside covering I used to turn the crumbly cake into a nice, flat, solid surface.
I ended up settling on this cake recipe, a raspberry filling, and a covering of chocolate ganache. I didn't like any of the fondant recipes I tried. None of them tasted good or seemed like something you'd want to eat. But later on I found a fondant recipe that uses white chocolate and corn syrup. You melt the white chocolate, add the corn syrup and it looks like some kind of cat barf. But then it magically smooths out in a few hours, and makes a delicious, easily workable fondant!
So I decided that I would put ganache on the cake first because ganache is delicious and structurally sound. Then a colorful layer of fondant would go over the ganache.
Step 4: R&D Labs 2 and 3!
In the next few R&D labs, I made bigger versions of the chosen recipes and worked on my ganache smoothing skills. I took careful note of how much the recipes made (one unit of the cake recipe makes 192 cubic inches of cake!).
I rolled out some fondant to the thickness I would use, and took a picture of it. I then brought the picture into CAD to see how much surface area there was, and compared that to what the CAD said the cake's surface area was to know how much I'd need.
I made some cake and undercut the sides, so they hung outward at a 45 degree angle, and let it sit for a day to make sure that it wouldn't fall apart.
The flame would be created from a metal container of 151 rum. I tested that to make sure it worked well and wouldn't melt the fondant near it (Using the actual metal frame, which in reality was being constructed in parallel with the R&D days).
I assembled some cake on the metal frame on one of the really cantilevered areas to double-double check that it wouldn't fall apart.
At the end if it all, I had a spreadsheet with all the ingredients I needed to make a 300 person cake, including 115 eggs, 24 quarts of heavy cream, 100 lbs of chocolate, and 20 lbs of butter.
Step 5: Design the Metal Inner Structure
Once I had a sense of the cake's structural properties, I could decide how much metal support to put in. For the main tower sections, I decided on a series of horizontal plates spaced at 3.5 inches, with some additional plates where things get super cantilever-ey. The top tower section where the fire was would be all metal, but covered in fondant to match everything else. The sides with the hearts would have bent sheetmetal to form all the bottom edges.
There would be a central pole running through. Spacers would slide over the pole in between the plate sections, so that the weight of the cake on each plate would be supported by metal and not the cake below it.
To make the cake transportable, I broke it into 3 major sections. Each section would have a square tube section at the bottom that slid over another, smaller square tube protruding from the section below. At the top of each section would be a welded in nut, and an eye hook would screw into that for lifting.
I drew all this in the CAD model, keeping everything inside the outline of the cake. Once it was all done, I processed the files for CNC plasma cutting.
Step 6: Honey! I Finished Welding the Wedding Cake!
I CNC cut the sheetmetal parts out of 16 ga mild steel. Not food grade you say? We'll deal with that soon enough!
For the curvy parts, I printed out a view of the shape at 1:1 scale, and then hand bent the parts to match the printout.
The base has a frame of 1x1 square tubing, and in the center there is a 3" length of 1x1 tubing sticking up. The curvy heart supports are also welded to the base assembly.
For the two tower sections, a 3.5" piece of 1 1/4" square tubing is welded to the first plate, and then a piece of 1" square tubing is welded on top of that. This slides over the 1" tubing sticking up from the section below, which makes things solid but removable.
None of the other plates on the tower sections are welded on. For serving, the plan would be to cut the top layer of cake and serve it, then slide off the metal plate it was on and start cutting the next layer down, and keep repeating until all the cake is served.
I then covered everything that would touch food in corn syrup, and applied aluminum foil over that. The corn syrup made a nice food-grade glue. Boy was that a yucky, sticky job though!
Step 7: Get Ready!
I started the baking process 4 days before the wedding. What a crazy month that was.
The first day of baking was focused on measuring all the ingredients and containerizing them into batches. Pre-measuring things and mixing the ingredients that could be mixed saved a bunch of time on the bake days. I also cooked up the raspberry filling and the fondant on this day.
Step 8: Bake!
I baked the cake in 6 batches. Each batch consisted of a 12x12x3 pan and a 10x10x3 pan. I pre lined the pans with parchment paper glued on with butter. This ensures that cakes come out very easily and very square. Because the pans were so deep, I cooked them at a 300 degrees so that the outside wouldn't burn before the inside was done. Each batch took about 2-3 hours to cook, which made for a few long days of baking.
When the pans came out of the oven, I cut the tops flat. This way everything is nice and rectangular, and there is no crust, only soft cakey goodness. I put a flat piece of metal over the pan and flipped it over, releasing the cake from the pan. The parchment paper stayed on the cake, which kept it fresh for the several day long baking process.
Step 9: Assemble!
This is where a bunch of big square cakes get made into a curvey tower. I cut the big squares into smaller building blocks to stack on the tower. It was a bit of freeform tetris. They don't have to be exact at this point, they want to be a little big so you can carve them to exact size later.
At this point, you have a bunch of 3" thick blocks. To make them delicious and layer-ey, I sliced them horizontally into 1" layers. To assemble, a layer of ganache goes on the the plate, then one of the 3 cake layers, then some filling, then another layer, and so on. The outside edges of the cake get ganache instead of filling between the layers to glue everything together, especially where things cantilever out.
Once an area of the cake is assembled, it should set for a few hours before doing anything more to it. This allows the ganache to harden up and prevents things from getting crumbly.
Once things are set on a whole area of the cake, it's time to carve it to it's final shape. A big serrated knife works well. Keeping the knife in hot water and drying it just before use helps too, the heat helps melt through the ganache.
When I carved the main tower sections, there were some gaps between the levels. I stuffed some of the shaved off slivers in there to take up the space and create a backing for the outer layer of ganache.
Step 10: Ganache!
Next, a layer of ganache goes over the cake. I did this in two steps: A rough layer and a finish layer. The rough layer should trap in any crumbs and fill in any areas that need extra volume.
Once the crumbs are trapped in by the rough layer, you can make things nice and smooth on the finish layer.
The ganache should be at a temperature where it is pastelike and not too runny so that it will stick in place and be workable. Keeping your ganache spreading tools in hot water helps them melt the ganache as you spread it and create a nice smooth finish (but you need to dry them off with a paper towel before use!). There are lots of good instructional videos on doing pretty ganache, they helped me quite a bit along the way although my technique isn't perfect yet!
Step 11: Fondant (or Not!)
I planned on covering the cake in black and pink swirly fondant stripes. However, time was getting short and I had a wedding to go to! So instead, I just added some accents in pink and left the ganache as the main surface. I wish I had the time to do the full fondant layer, but was still pretty happy with the results!
Step 12: Add Fire!
Caution: The burning liquid can spill from the container and burn you/whatever it lands on! Do not move or wobble the cake with the fire burning! Be sure to have a large, flat piece of metal ready for putting the fire out. Be sure to light it with something like a torch or long match, something that allows your hand to be far from the flame.
The fire comes from a metal container of 151 rum in the top of the cake. I used a 28oz tomato can, and burned it in beforehand so that no stinky, smokey stuff would be still on it come wedding time. The surface area was enough for a good flame(too narrow of a container and the fire will starve itself of oxygen and be very small). I filled it up nearly all the way, which turned out to burn for quite awhile, perhaps too long. I ended up putting the flame out by covering it with a piece of metal.
I also packed ice around the flame container so that the fondant covering on the outside of the cake top wouldn't melt.