Prepare the ingredients. Wash the orange well and grate the peel. Squeeze the orange, and set aside the juice. Separate the egg yolks and egg whites into different bowls.
Make the meringue with the ingredients marked . First, add a pinch of salt to the egg whites, then beat in the sugar and baking powder in two batches using an electric mixer. Beat until firm peaks form. Be sure that it's really stiff! Set aside.
For the ingredients marked : First, beat egg yolks and sugar with a whisk until light-colored. Add olive oil, orange juice, peel, and skim milk powder, and blend well with an electric mixer.
Add okara and continue mixing until the batter is thick. Switch to a rubber spatula and fold in the meringue from Step 2, half at a time. Avoid breaking the meringue bubbles and carefully incorporate into the batter.
Pour the batter into a chiffon cake tin and bake at 300-320F/150~160C for about 45 minutes. When it's done, take it out of the oven and immediately turn it upside down to cool. This prevents sinking.
This is a circular cake I made by halving the recipe. It turned out like a light sponge cake. You can use it as a base and decorate it in many ways. It's not very tall, since I halved the recipe, but If you use the whole recipe you can make a layer cake.
This time I made it into a strawberry shortcake. I doubled a recipe for yogurt cheese cream and added 200 ml of whipped cream. I divided a chiffon cake in two, and put a layer of the cream and strawberries in the middle.