Prepare the ingredients. Separate the eggs into yolks and whites. Mash a banana with a fork. Sift cake flour through a sieve in advance. Preheat the oven to 340°F/170°C.
Add 1/2 of the soft light brown sugar to the egg whites and whip up stiffly with an electric whisk with the highest speed. Don't wash the electric whisk, use it to whip up the egg yolks...
Add the rest of the soft light brown sugar to the egg yolks and whip until white and thick. Then add the mashed banana and continue whipping.
When the banana lumps are mostly gone, add soy milk, safflower oil and mix well. Then add cake flour and continue mixing.
When the flour is thoroughly mixed, add egg white to the egg yolk dough in 3 to 4 portions (Use the lowest speed for the electric whisk or switch the electric whisk off and stir by hand)
Mix up from the bottom using a rubber spatula and pour the batter in a cake pan.
Bake in an oven for about 40 minutes and turn it upside down to let it cool. The picture is from baking for about 20 minutes. If you're worried about burning the surface, cover with aluminum foil on top.
Story Behind this Recipe
My kids said that they were not quit happy with plain chiffon cake, so I added banana and soy milk to make a hearty and healthy version.
I used electric whisk for the entire process. When you start with the egg whites, you can use it again without washing. When mixing the egg whites, it's easier to mix than with a rubber spatula. Try not to mix too much to maintain the airy texture. If you don't have safflower oil or soft light brown sugar, vegetable oil and caster sugar should be OK.