Sift the cake flour once and set it aside. Preheat the oven to 170°C. Beat the whole eggs and yolks together.
In a sauce pan over medium heat, melt butter until it bubbles. Add the sifted cake flour all at once.
Over medium heat, mix the butter and flour well. Continue heating until the mixture becomes satiny and starts to thicken. (Do not scorch).
Remove from the heat. Pour the egg mixture 1/3 at a time stirring well each time using an electric mixer at high speed.
Microwave the milk to the point that steam starts to come out. Pour it into Step 4 and combine well. Add about 10 drops of vanilla oil.
In a bowl, beat the egg white with an electric mixer at high speed. When the egg white starts to cling to the whisk, add half of the granulated sugar and beat more.
Beat until soft peaks form, add the remaining sugar and make it into a meringue.
Add 1/3 of meringue into the bowl from Step 5, combine well with electric mixer. Add the remaining meringue 1/3 at a time.
Stop beating when the meringue starts to form fine lines. Gently mix the meringue. Do not over-beat (I forgot to take a photo) .
Pour the batter into a parchment paper lined baking pan. Smooth the surface of the batter.
Bake in 170°C oven for about 12 minutes. When the baking is done, cover the pan with plastic wrap until cool.
When it's completely cooled down, slice off one of the edges diagonally about 1cm from its end. Place the cake onto a sheet of a paper so that the sliced end will be the outer most part of the cake.
Spread your favorite filling on top (the closer edge should have a thicker layer of filling and gradually lessen the amount to spread).
Start rolling by tucking the edge tightly into the center, creating the core of the roll. Hold onto the rolling paper, roll it up all at once by pulling the paper diagonally ahead of you.
Cover it with plastic leaving the rolling paper on. Let it cool completely in a refrigerator.
The filling of the main photo is diplomat cream which is a mixture of custard cream and whipped cream. The photo here has whipped cream only.
Story Behind this Recipe
I tried this recipe because I wanted to make a smooth and yet filling roll cake.
By bringing the butter to a complete boil, combining with flour really well will allow the eggs and milk to be incorporated into the batter. If this process doesn’t go well, the batter becomes watery and the end product will have a rubbery texture.