Matcha + azuki red beans is a ubiquitous flavor combination in Japanese desserts because they are such a match made in heaven!
Matcha is a green tea powder made of ground up whole tea leaves. Primarily, it is a rich source of antioxidants among other health benefits and is delicious with its fragrant and mildly bitter taste. It is so simple to incorporate matcha into baking! For this cake, I simply substituted 3 tablespoons of matcha powder in place of all purpose flour to convert my all-time favorite vanilla cake into a matcha cake.
For the azuki (aka adzuki) red beans, I use the Shirakiku brand of prepared sweetened red beans but any brand will do. You can also make your own by cooking dry azuki red beans and sweetening it with sugar or other sweetener of choice. Bob's Red Mill is a popular brand that sells the dry bean (make sure it is azuki or adzuki and not "regular" red bean as they are not one and the same). If you cannot find either canned or dry, or the idea of beans in your cake weirds you out, you can omit it and the matcha cake is still divine!
MAKE AHEAD + OTHER NOTES:
- Swiss meringue buttercream can be stored up to 4 days at room temperature, 2 weeks in the fridge or 2 months in the freezer. When you bring the buttercream out of fridge or freezer, bring to room temperature several hours or a day before and revive it by mixing it with the paddle attachment of your stand mixer on low-medium speed. It will first appear broken or curdled but will eventually come back together.
- Cake layers (unfrosted) can be made a day or two ahead, wrapped tightly in plastic wrap & inside a zip top bag, stored at room temperature. Store in the fridge if making 3-4 days ahead, or store in the freezer if longer than that. To use, unwrap and bring to room temperature.
- Frosted and uncut cake can be stored at room temperature for 4 to 5 days. A frosted cake requires no plastic wrap - simply keep it under a cake dome, overturned bowl, clean box or microwave (not "on"!) to keep dust away. However, the more "naked" the cake (i.e. thinner frosting) the faster the cake will dry out in which case do put plastic wrap directly all the way around the side of the cake; typically the top of naked cakes have a good amount of frosting so you can still keep the top wrap-free, so as not to ruin your pretty designs.
- Cut cake should be wrapped tightly in plastic, especially the exposed cut sides where moisture will escape. "Harden" the frosting by placing the cake in the fridge for 15 minutes first, then wrap it up tightly, not just loosely tented. It can be kept at room temperature for 3 to 4 days, or the fridge for a week.
Matcha Cake with Azuki Red Beans + Vanilla Swiss Meringue Buttercream
Recipe makes one 3-layer 9" cake OR 4-layer 8" cake.
For the cake layers
3 3/4 C (431g) Less 3 tbsps all purpose flour
3 tbsp matcha green tea powder
3/4 tsp baking powder
3/4 tsp baking soda
1 tsp salt
1 1/2 C (3 sticks; 345g) unsalted butter, room temperature left out of fridge 3 hours
1 1/2 C (280g) granulated sugar
4 large eggs, room temperature
2 large egg whites, room temperature
3 tsp (15ml) pure vanilla extract
1 1/2 C (360ml) buttermilk*, room temperature
*If you do not have buttermilk, make your own by putting 3 tsp of vinegar into a measuring cup and adding enough whole milk to make up the 360ml required in the recipe. Stir and let sit 5 minutes before using.
For the swiss meringue buttercream
6 large (180g) egg whites
1 1/2 C (300g) granulated sugar
1 1/3 C (160g) confectioner's sugar, or to taste**
2 3/4 C (624g) unsalted butter, room temperature (out of fridge for 3 hours), or to taste**
1 tbsp vanilla bean paste or pure vanilla extract
**The amount of confectioner' s sugar and butter can both be adjusted "to taste" with the following guidelines:
- For the confectioner's sugar, you can use as much as 2 C or 240g in total.
- For the butter, it can be reduced to 2 1/4 C or ~512g in total (i.e 1/2 C or 8 tbsp less than the stated amount). Don't be afraid to taste it until it's just right!
For mixing in with the buttercream in between cake layers (optional)
1 can 7.4 oz (120g) prepared sweetened azuki / adzuki red beans (see also recipe intro above)
For the cake layers
1. Preheat oven 350f. Grease and flour 3 x 9" round cake pans (or 4 x 8" round cake pans). Wrap the cake pans in wet towel strips to minimize doming during baking.
2. In a large bowl, measure out the 3 3/4C (or 345g if using a scale) of the flour and scoop out 3 tablespoons of it. Add back in 3 tablespoons of matcha green tea powder. Add the baking powder, baking soda and salt. Whisk everything very well and set aside.
3. In a stand mixer with the paddle attachment, beat the butter until smooth & creamy, about 1 minute.
4. Add sugar and beat on high speed for 5 minutes until creamed very well. Scrap down sides.
5. On medium-high speed, add 1 whole egg at a time, beating well after each addition until all 4 whole eggs are mixed in.
6. Beat in vanilla, Scrap down sides.
7. On low speed, add dry ingredients in 3 additions, alternating with the buttermilk. Do not overmix! The batter should be smooth, velvety and slightly thick. Transfer to the large bowl that previously held the dry ingredients.
8. Change to the whisk attachment on the stand mixer. Vigorously beat the 2 egg whites until thick and foamy, approximately 3 minutes.
9. Fold egg whites gently into the batter.
10. Divide equally into prepared cake pans. [Optional but recommended: wrap the cake pans in wet towel strips to minimize doming during baking. You can see how I did this in my Black Forest Cake post and I also demo'd it on theFeedfeed's snapchat here ]. Bake ~25 min for 9" pans OR ~23 min for 8" pans, or until a toothpick inserted in center of cake emerges dry with crumbs clinging on. Do not overbake! Since ovens vary so much, always test doneness a few minutes prior to the stated bake time for any baking recipes you're making the first time. In my gas oven, my 8" cakes are actually done perfectly at 20 minutes.
For the Swiss meringue buttercream
11. Over a double boiler, whisk in granulated sugar and egg whites, stirring and moving everything around constantly, until mixture reaches 115f and sugar grains are completely dissolved. Gretchen (author of this buttercream recipe) suggests to put on a pair of disposable gloves and use your fingers to move the mixture around and feel the sugar grains until they have just dissolved - I prefer this method as well as it is much more reliable than my faulty candy thermometer.
12. Pour mixture into metal bowl of your stand mixer fitted with the whisk attachment. Whip on high until thick, glossy and white (very firm peaks), about 4 minutes.
13. Meanwhile, sift confectioner's sugar. Once the egg whites are done, turn the stand mixer to the lowest speed and add the confectioner's sugar all at once. Let the whisk turn a few times to settle the sugar before increasing mixer speed to medium-high and whisking until everything is even.
14. While the mixer is still running on medium-high, add the room temperature butter in about 2 to 3 fast additions. You may wish to reserve 1/2 to 1 stick of the butter to add "to taste at the end, as explained previously at the end of the "Ingredients" section.
15. Add the vanilla. Now taste the buttercream to see if it is to your liking (sweetness and buttery-ness) and add more as needed, following my guidelines above. Mix until thoroughly combined.
16. Switch to the paddle attachment and blend on low speed until the buttercream is smooth, about a minute.
Assembling the cake
17. If needed, level out the tops of your cooled cake layers with a long serrated knife. If you used the wet towel trick, then you should be able to skip this step entirely!
18. If using asuki red beans in your cake, separate about 3/4 of the buttercream and stir in the red beans until even. Set aside the remaining 1/4 of the buttercream to be used on the top and outside of the cake.
19. On a cake board or cake stand lined with 2-3 pieces of parchment (that can be removed once the frosting is done), place bottom cake layer in the center, right-side up. Scoop about 1/3 of the azuki buttercream into the center and spread it out evenly with a spatula. Continue with the remaining 3 cake layers, stacking the second layer upside-down, the third layer rightside-up and final fourth layer upside-down again. If you are making a 3 layer cake, alternate similarly. Just make sure you end up with an upside-down cake layer at the end so you get a nice flat top. Make sure all the layers line up nicely before continuing.
20. Frost the top and side of the cake with the remaining buttercream. For a prettier finish, do a crumb coat first - that is, spread a thin layer of buttercream and refrigerate for 10-15 minutes (but not longer) to firm up then spread the remaining buttercream on, smoothing everything out with an offset spatula and side scraper if you have one. The sides of this cake is semi-naked, meaning it is not completely frosted and you can see bits of cake layers peaking out.
21. Finally the fun part! Decorate the top with edible flowers, chocolates or whatever you have in the snack cupboard. On mine, I have red carnations (I like to wrap the parts touching or inserted into the cake with plastic wrap first), Royce matcha chocolate cookie sticks, Royce matcha chocolate squares, Lindt white chocolate balls and a little wee dusting of matcha powder :)