Cold Brew Tiramisu Layer Cake
Tiramisu is one of my favorite desserts, as is of course the majestic layer cake. Smush them together and this is what you get!
I am excited about this cake for a whole handful of reasons. For starters, I discovered a product that has made painting on gum paste easier and more intuitive for somebody who works with watercolor (yo). It's called Edible Art Paint by a company called Sweet Sticks, and you just shake it up and it's ready to go! I've been mixing colors, doing some layering, and also using edible markers on top of the dried paint (more on that coming soon) to great effect. The paint is made in Australia, but the Sweet Sticks website lists distributors in other countries, including the US.
I decided to paint a giant coffee bean as my first experimental project (I'll post a video of how I did it soon), and it came out better than I could have hoped. That texture! I also found out that you can paint coffee beans with the Sunkissed Gold color and they look like they're solid gold. So many possibilities!! I'm still getting used to the quirks of the paint, but man! I'm totally head over heels for it.
I am also excited about this cake because I found some neat ways of capturing the flavor of a tiramisu cake in layer cake form. The question was how to give structure to a dessert that is so soft and luscious that it needs to be served out of a low, flat dish. The answer was surprisingly straightforward: instead of individual ladyfingers as a base, I baked a genoise cake (which is basically the same thing) and torted it into layers. I didn't soak the layers quite as much as you want to soak the ladyfingers in a tiramisu because I was worried about structural integrity, but I did give each layer a solid brushing with a combination of Kraken rum, cold brew coffee, and simple syrup infused with real cinnamon; my fiancé is an amateur tiki mixologist and I am lucky enough to have stuff like that lying around the house!
Then I just straight up added mascarpone to Vanilla Bean Italian Meringue Buttercream in a ratio of 1:4, which allowed me to get that fresh creaminess from the soft cheese while preserving the load bearing properties of the buttercream. Hurray!
The best part, however, was easily the Cold Brew Italian Meringue Buttercream on the outside of the cake. I mean, dang. Cold brew has a strong flavor with more a pronounced fruity and acidic profile than the chocolatey, caramely notes in heat-brewed coffee. That citrusy flavor leant a sophistication to the buttercream that was totally unexpected and DELICIOUS. Do yourself a favor—make this buttercream! The recipe is below.
Strong Cold Brew
90g (a generous cup) course-grind coffee beans (I used Italian roast to fit the theme, but use whatever you like!)
945g (4 cups) water
Mix the coffee into the water and set aside, either in the fridge or on a counter, for 24 hours. Strain (I used a metal sieve first and then strained again through cheesecloth) and set aside, doing your best not to drink more than like half a cup before getting started with the cake.
Cold Brew Italian Meringue Buttercream
Note: You can easily halve this recipe, which may make more sense if you're only planning on frosting the outside of a single cake with it like I did for my tiramisu cake. That said, extra buttercream it is never a bad thing to have on hand, and you can always freeze it!
480g (2 2/3 cups tightly packed) dark brown sugar
119g (1/2 cup) cold brew
7 egg whites (or 14 tsp egg white powder reconstituted with 14 Tbsp cold brew)
1 tsp cream of tartar
905g (2 lbs; 8 sticks) unsalted butter at room temp
2 Tbsp vanilla extract
Optional: A couple Tbsp coarse ground coffee for enhanced visuals
Special equipment: a candy thermometer or instant-read thermometer
Place the brown sugar and 119g cold brew in a deep pot, deeper than you would normally use for boiling a sugar syrups. This is important; brown sugar syrup boils up much higher than white sugar syrup, so not only will it behoove you to use a medium-large pot to cook it in, you'll also want to keep a vigilant eye on it to make sure you adjust the temperature down as necessary to prevent a messy boil-over situation.
Place the pan over medium heat, stirring occasionally until the sugar melts, and insert a candy thermometer. As soon as the syrup starts to bubble, reduce the heat to low or medium-low; feel it out, see what level of heat the sugar can take without going over the top.
While keeping an eye on the syrup, start to whip the egg whites in a stand mixer at medium speed using the whisk attachment. When the whites are frothy, add in the cream of tartar and turn the mixer up to medium-high speed to achieve stiff peaks. You don't want to over-whip the whites, so if they are nearing stiff peaks and your sugar isn't at the right temp yet, slow your mixer so you can try to synch things up as best you can.
When the sugar reaches 235°F (113°C), remove it from the heat and slowly pour it into the egg whites, whisking at high speed. Usually recipes will say to whisk on high until the meringue cools to room temperature, but honestly, that always seems to take forever, so once my meringue is looking stiff and luxurious, I'll just take it off the mixer and stick the bowl in the fridge or freezer until it cools down enough that it won't melt the butter.
Once the meringue is no longer warm to the touch, switch to a paddle beater and add the butter in half a stick at a time, beating at medium speed. Once all the butter is incorporated, continue to beat at medium for another few minutes; the buttercream will be light as a cloud and fluffy af. Add in the vanilla and a few tablespoons ground coffee if you want some speckles of coffee to liven up the look of the buttercream. It's ready to use!
Note: For the Mascarpone Buttercream I used in this cake, I took four cups of leftover plain vanilla IMBC I had lying around and added 2 tsp vanilla bean paste and 225g (1 cup) mascarpone. You can do the same thing with 4 cups of cold brew buttercream if you don't want to go to the trouble of making a plain batch too, you just won't achieve the difference in color that makes slices of my version so pretty.