Matcha Gateau au Chocolat

Before You Start...

1. Please note that this cake requires a cooling time of 4 hours. Once cooled, you can serve it or chill it overnight in the refrigerator.
2. Gather all the ingredients. I highly encourage you to weigh your ingredients using a kitchen scale for this recipe. Click on the “Metric“ button at the top of the recipe to convert the ingredient measurements to metric. If you‘re using a cup measurement, please follow the “fluff and sprinkle“ method: Fluff your flour with a spoon, sprinkle the flour into your measuring cup, and level it off. Otherwise, you may scoop more flour than you need.
3. Preheat the oven to 350ºF (180ºC). For a convection oven, reduce the cooking temperature by 25ºF (15ºC). Line a 6-inch (15-cm) round cake pan with parchment paper (I use a 6- x 3-inch pan). I spray oil on the pan first so the parchment paper will stick to the pan. Note: If you’re using a larger pan, see the Cake Pan Size section of my blog post for how to adjust the recipe.

To Mix the Batter

1. Break or chop up 3.5 oz white chocolate into smaller pieces and put them in a heatproof large metal or glass mixing bowl (make sure the bowl is moisture- and grease-free).
2. Cut 3 Tbsp unsalted butter into small cubes and add to the bowl with the white chocolate.
3. To set up a double boiler, bring 2 inches of water in a pot to a gentle simmer and then rest the bowl with your ingredients on the pot. You want it to fit snugly without touching the water. Melt the chopped white chocolate and butter in the double boiler.
4. With a silicone spatula, mix and let the chocolate and butter melt completely.
5. Carefully remove the bowl from the double boiler. Make sure the steam or water doesn‘t get into the chocolate mixture or the chocolate will seize up. Add 3 Tbsp matcha (green tea powder) and mix them all together completely with the spatula, making sure there are no lumps.
6. Gradually add ¼ cup whole milk as you stir. Mix it together well.
7. Separate the egg whites and yolks of 3 large eggs (50 g each w/o shell). Put the whites in a small bowl and the yolks in a large bowl. Refrigerate or freeze the bowl with the egg whites for 15 minutes until cold. (It‘s okay if the egg whites are partially frozen). Tip: In Japan, we chill the egg whites to make smooth, fine-textured meringue and do not use cream of tartar.Next, add 3 Tbsp sugar to the bowl with the yolks.
8. Whisk the egg yolks and sugar vigorously with a hand whisk until the mixture is a creamy, pale yellow color.
9. Add the matcha chocolate mixture to the egg yolk mixture and mix the batter well.
10. Use a flour sifter or fine-mesh sieve to sift 3 Tbsp cake flour into the batter.
11. Gently whisk the cake batter until the flour is just incorporated. Do not overmix.
12. Add ⅛ tsp Diamond Crystal kosher salt and mix it all together.

To Make the Meringue

1. Remove the egg whites from the refrigerator or freezer and add them to a clean, large bowl. Using an electric hand mixer or a stand mixer with a whisk attachment, start whipping the egg whites on medium-low speed (or Speed 4 on a KitchenAid stand mixer) until the egg whites are bubbly, opaque, and foamy.
2. Gradually add 3 Tbsp sugar to the bowl while beating. Then, increase the mixer speed to high (or Speed 10 on a stand mixer). Beat vigorously until stiff peaks form (see the next step for how to check). It takes about 2 minutes of beating at high speed to reach stiff peaks. Tip: When using a stand mixer, I usually pause beating when the egg whites are almost done. I take off the whisk attachment from the mixer and use it to hand-mix the looser egg whites near the bowl‘s edge into the stiffer whites near the center until it‘s all homogenous in texture. Then, put the whisk back on and continue beating.
3. To check for stiff peaks, pull up your beaters or whisk. The meringue in the bowl or on the beaters/whisk should be firm enough to hold a peak, pointing straight up (or maybe folding over a little bit just at the very tips). By this time, the meringue should have a glossy texture, too. Tip: If you overbeat the meringue, it will become very stiff and grainy and won‘t incorporate into the batter at all.

To Fold In the Meringue

1. Using the spatula or a hand whisk, add one-third of the meringue into the batter. Mix well by hand until it‘s homogeneous.
2. Gently fold in another one-third of the meringue. Take care not to deflate the air bubbles in the meringue and batter as you fold. Finally, add the remaining whites and repeat the folding motion until the foam is just incorporated. Take care not to deflate the air bubbles in the meringue and batter as you fold. Once it's well combined and homogeneous, fold the batter one last time and scrape the sides and bottom of the bowl to make sure there is no chocolate accumulation. The final batter should fall in ribbons when you lift the spatula or whisk.

To Bake

1. Transfer the cake batter into the prepared cake pan. Smooth out the surface with the spatula.
2. Bake at 350ºF (180ºC) for 15 minutes, then reduce the temperature to 325ºF (160ºC) and bake for another 20 minutes. When the cake is done baking, the center will still wobble slightly. The inside of the cake will be soft and moist, so you can’t insert a skewer to check doneness. Remove the pan from the oven and set it on a wire rack to cool completely, about 4 hours (otherwise, it‘ll be impossible to cut). If you‘d like, you can cover the cooled cake and keep it in the refrigerator overnight.

To Serve

1. Remove the cake from the refrigerator (if you‘ve chilled it) and slice the cake. I highly recommend warming the chilled cake slices in the microwave for 5 seconds. Dust 1 Tbsp confectioners’ sugar on top, if you‘d like, and serve. The cake literally melts in your mouth!

To Store

1. You can keep the cake in an airtight container and store in the refrigerator for 3 days and in the freezer for a month.