Measure out the granulated sugar, vegetable oil, and cake flour. Separate egg yolk and egg white into different bowls. Preheat oven to 170℃.
Blend a banana and 20 ml of milk in a food processor. Blend completely until nothing is solid.
Into the bowl of egg yolks, add half the granulated sugar in three batches. Whip well until thick as in the photo.
Add vegetable oil, then add the blended banana in 3 batches. Mix well.
Sift in the flour in 2 batches and fold in with a rubber spatula. Fold in lightly, working from the center towards you and bottom-up. Make sure the bubbles don't disappear.
It's best if the batter is glossy.
Into the bowl of egg whites, add the rest of the granulated sugar in 3 batches and beat well. Whip until the beaters can stand up.
It should become glossy. The egg whites will separate if whipped too much, which prevents the batter from rising enough.
Add a third of the egg whites into the bowl from step 6. Mix it around.
Add the rest of the egg whites in 2 batches and mix. Again, fold in lightly working from the center towards you, and bottom-up.
Pour batter into the mold from the same direction, if possible. Shake the mold to smoothen out. Drop onto your workplace a few times from a height of 10cm to remove any air bubbles.
Bake for 40 minutes at 170℃. Test with a bamboo skewer. If it comes out clean, then the cake is done. Flip the mold over and cool it down on a wine bottle. Cool for several hours.
Please adjust the baking time to your oven. If your banana isn't ripe, add 5 g of granulated sugar.
Story Behind this Recipe
I've been making quite a few chiffon cakes ever since I started buying my eggs directly from the poultry farm. Every time, I try adding different kinds of ingredients into the cake. I'm looking forward to posting some of those recipes here if it turns out nicely.
If the top is going to burn due to the height of your oven, cover it with aluminum foil. Because you use milk instead of water, the cake turns out really moist. When preserving, please wrap with plastic wrap and freeze in a freezer-safe zip bag. Defrost to serve. This way, you can keep the cake for a month.