Test Kitchen - Green Tea Opera Cake

When I make the mistake of choosing a Test Kitchen ingredient that is already a full product on its own, it becomes difficult to come up with ideas on what to do with it. Several of you lent your suggestions over on Facebook but I have to say, nice try but sorry, I'm not sending everyone the delicious Dark Matcha chocolate bars, haha. If I had an unlimited supply, I would but alas, my coffers were reserved for making something. So I thought and thought and though I wanted to avoid going the dessert route, it ended up being the way to go. However, a challenge must be a challenge so I opted for a type of baking I haven't done before - I wanted to make those light and fluffy cakes I see in Asian bakeries. After some snooping around the internet, I came across what was called an opera cake and was basically what I was looking for. The inspiration came from this recipe here which is a coffee and chocolate version but I green tea-ed it completely for a delicious and different approach. It requires multiple steps but oh, trust me, it's worth it.

Step 1: Ingredients (yields two layered 4.5" x 6.5" cakes)

Almond Cake
  • 2 large eggs, room temperature
  • 1 cup almond flour/meal
  • 1/2 cup powdered sugar
  • 3 Tbsp cake flour (alternatively, sift 1 tsp cornstarch with a little less than 1/4 cup all-purpose flour)
  • 2 large egg whites, room temperature
  • 1/8 tsp baking powder
  • 1/8 tsp salt
  • 1 Tbsp sugar
  • 2 Tbsps unsalted butter, melted and foam removed

Green Tea Syrup
  • 1/2 cup water
  • 1/2 cup sugar
  • 2 bags green tea

Vanilla Buttercream
  • 1/4 cup water
  • 6 Tbsps sugar
  • 2 large egg yolks
  • 1 Tbsp vanilla extract
  • 1/2 cup unsalted butter, 1/2" cubes and softened

Green Tea Chocolate Glaze
  • 7.5 oz dark matcha green tea chocolate, roughly chopped
  • 1/2 cup unsalted butter

Step 2: Prepping the batter
Beat whole eggs on high in a mixing bowl until it triples in volume and gets frothy. Turn to low and beat in almond flour and powdered sugar. When that is ready, fold in your cake flour (if you don't have cake flour, mix in 1 tsp of cornstarch to a little less than 1/4 cup all-purpose flour) gently. In a separate bowl, beat egg whites on high until foamy. Add in baking powder and salt until soft peaks can be formed.

Step 3: Finishing the batter
Line a 9x13 baking dish with parchment paper; leave overhang. Preheat oven to 425°F. Into the egg whites, add your 1 Tbsp of sugar and beat until stiff peaks form. In a separate bowl, melt butter and remove foam. Let cool. Fold the egg whites into the almond flour mixture 1/3 at a time. When the butter has cooled, fold that gently in as well. Pour into baking dish being careful to flatten it out and not let it deflate. Bake for 8-10 minutes.

Step 4: Making the syrup
(Remove cake from oven when done and let cool) Boil water with sugar until sugar has dissolved. Steep green tea bags for a few minutes in the boiling syrup. Taste for your preferred strength of green tea taste. Discard tea bags and let cool.

Step 5: Making the green tea chocolate glaze and buttercream
You can either use a double boiler or be lazy like me and use the microwave. Either way, gently melt together chocolate and butter, stirring frequently to make sure they are incorporated well. If using a microwave, melt in 25 second increments.

For buttercream, boil 1/4 cup water and 6 Tbsps of sugar together until they reach 238°F (soft ball stage). I had to tilt my candy thermometer so the bulb would touch the shallow liquid. Beat your egg yolks on medium for one minute before slowly adding in hot syrup (constantly beating) so as not to cook the eggs. Add in vanilla extract and beat until cool. Then, one at a time, add in 1/2" cubes of softened butter and beat until a smooth and thick cream emerges. Harden in the fridge.

Step 6: Assembly and finishing
Slice the finished cake into even fourths, removing edges so the layers will stack on each other perfectly. Brush your first layer with green tea syrup until absorbed. Then add green tea chocolate glaze all the way to the edges. Let it set before placing another cake layer on top. Brush that with syrup again. Next, add buttercream on top. For picture purposes, I had covered the entire cake structure with the buttercream but you don't have to. Refrigerate to let set while you think of your design with the glaze on top. I did a simple band with shaved green tea chocolate all around. Decorate once the buttercream has hardened enough. Enjoy!

The next Test Kitchen ingredient: red rice
"Red rice is a special variety of rice that looks red in color, thanks to its anthocyanin content. It is generally unhulled or partially hulled rice which has a red husk, rather than the much more common brown. Red rice has a nutty flavor, and a high nutritional value, as the germ of the rice is left intact." [Wikipedia]

You know the drill! Let us know what you think we should or could make with it. We don't need full recipes - just an idea will do and we'll post it later.

Photography by Duc Duong.