Combine the cake flour and matcha green tea powder and lightly mix in a bowl. Then, sift the flour with a mesh strainer. Repeat this 2 to 3 times to help avoid pockets of flour and also to make the cake light and fluffy.
Let’s make the batter for the roll cake. Using a hand mixer, beat 4 egg whites in a bowl. When the white is foamy as shown, add half of the sugar. Beat it again and then add the rest of the sugar.
Beat until the meringue reaches a stiff peak stage. Lift the beaters to check if the stiff peaks form.
Remove the meringue from the beaters. Then, lightly beat the 4 egg yolks in a bowl. Add the sugar and continue to mix.
Make sure to beat the egg whites first otherwise the remaining yolk on the beaters will ruin the meringue. Beat the yolk until thick and creamy.
Add the sifted flour to the yolk. Using a balloon whisk, mix until the flour is completely moistened.
Add 1/3 of the meringue.
Lift the mixture with the whisk and drop it into the bowl. Repeat this to mix the batter thoroughly.
When combined, add the rest of the meringue in 2 steps. Lift the mixture and drop it into the bowl.
Repeat this mixing process about 100 times while gradually rotating the bowl. Try not to break the foam. The batter will get glossy and smooth.
Pour the batter into the baking sheet covered with the Kraft paper.
With a scraper, distribute the batter to the edges. Be careful not to break the foam and gently spread it evenly. Drop the baking sheet a few times to break any air bubbles in the batter.
Place it in the preheated conventional oven and bake at 170°C (340°F) or for about 25 minutes. When 12 to 13 minutes passes, rotate the baking sheet 180 degrees, reversing the left and right sides. This will help to bake the sponge cake evenly.
Now, remove the baking sheet from the oven. Drop it a few times to prevent the sponge cake from shrinking.
Remove the cake and place it onto a flat surface. To keep it from drying, cover with another baking sheet or aluminum foil and let it sit to cool.
Let’s make the matcha roll cake. Whip the cream to stiff peaks and add the azuki bean paste. Mix it evenly, making firm azuki cream.
Release the edges of the paper from the cake. Cover the top of the cake with another sheet of paper and then flip it over. Carefully, peel off the paper from the bottom of the cake.
Place the paper on the bottom again and then flip the cake over.
Using a knife, cut off the edge with a diagonal cut. This will help to close the seam, making the shape of the roll cake look beautiful.
Place the azuki cream onto the cake. Distribute the cream with an icing spatula. Coat it a bit thickly on the uncut side since the near side of the edge will go to the center of the roll cake.
Sprinkle on the sweetened azuki beans.
Fold the edge of the cake and then push the paper forward, rolling the cake.
Remove the paper and wrap the roll cake with another sheet of paper. Using a ruler, tightly wrap the roll cake as shown in the video. Make sure to place the cake with the seam-side down.
Cover it with plastic wrap and let it sit in the fridge to cool.
Now, the matcha roll cake is ready to serve. Unwrap the plastic wrap and the paper. Sprinkle on the powdered sugar.
Wipe the blade of a knife with a dampened towel and cut out a slice.
Make sure to use a clean bowl and beaters to help foam up the meringue.
Cocoa or instant coffee powder can be added to the batter instead of the green tea powder.
You can also use your favorite fruits as fillings if the sweetened azuki beans are not available.
Bakery paper can be also used but you can remove the Kraft paper from the cake more easily.