Combine cake flour with matcha and sift. Warm the milk to body temperature. Preheat the oven at 340°F/170°C.
Finely chop the white chocolate and coat with cake flour. You could also use mini chocolate chips.
Separate the egg yolks and egg whites, and chill the whites in the fridge. Add granulated sugar to the yolk and whisk until it turns pale.
Add vegetable oil to the bowl from Step 3 and mix well. Stir in the milk. Add the powdered ingredients and whisk well.
Add a pinch of salt to the egg white. Add granulated sugar in small batches and whisk. When it's whipped, add the remaining granulated sugar.
Make a fine and glossy meringue. Stop when the egg whites form peaks with tips that curl over when the whisk is lifted. Blend at low speed.
Stir in 1 spoonful of meringue into the egg yolk dough with a whisk and blend.
The meringue will dry up quickly, so make sure to keep whisking.
Add half of the remaining meringue into the dough from Step 7. Stir lightly and gently with a rubber spatula.
Add rest of the meringue into the mixture from Step 9 , then mix and spoon. Stir gently until the egg yolk and egg white is completely blended.
Knock off excess flour from the white chocolate and add to the batter. Mix lightly and pour into the mold. Stop when it's about 80% full.
Stir about 3 times with a chopstick. Hold the sides with both hands and shake. Make sure the batter covers all sides of the mold.
Bake 20 minutes at 340°F/170°C, then 15 to 20 minutes at 320°F/160°C. Test with a skewer and make sure it comes out clean.
Turn over the mold immediately and let cool on a bottle, or something stable. When it's slightly cooled, cover with a plastic bag to avoid drying up. Remove from mold when it's completely cooled down.
Note: it's alright not to add white chocolate. If you opt out, add 20 g of sugar to the yolks.
Here's the basic chiffon recipe Recipe ID: 1472541
Story Behind this Recipe
I posted a matcha variation of the basic chiffon cake before, but this is a version with white chocolate chips.
I used mini chocolate chips. The melting point of chocolate depends on whether it's confectionery or normal bar chocolate. Also, finely chop it, otherwise it will cause air bubbles. As matcha absorbs moisture, the batter may be stiffer than you expect. Make sure it's soft and runny before pouring into the mold.