Raspberry Swiss Roll (Bolu Gulung)

I grew up eating this rolled sponge cake thingy that we call Bolu Gulung (which by the way, it literally means rolled sponge cake. Brutal translation, I know). Honestly, the best part of this cake is because it's so simple and versatile. You can fill it with whatever you want. The key of a good Bolu Gulung is on the cake itself. It has to be soft and fluffy.

It was only a few weeks back that I realized that Bolu Gulung is actually the same thing as Swiss Roll.. Hahahaha.. Dunno why it never occured to my mind the resemblance of these two cakes means they are actually the same thing. Silly me. 

I remember back when I was a kid, there was this Bolu Gulung frenzy, especially the one sold by Meranti shop in Medan. It was like the 'it' cake. Well, their Bolu Kukus was indeed really good, and my fav was the one with cream cheese feeling. I wonder if they still exist tho, I must check it out next time I come home to Indonesia, for the sake of childhood memory. 

Today I made Bolu Gulung, or should we say Swiss Roll with raspberry butter cream filling. To make the roll cake takes a bit of patient, you have to really whip the egg whites properly. An electronic mixer would be really helpful in this case, unless you have a some muscles. 

Let's begin, shall we?

Cake ingredients:
4 egg whites
1 tsp white vinegar
60 gr sugar
4 egg yolks
40 ml oil (I used canola oil)
40 ml milk
1 tsp vanilla extract
1/4 tsp freshly ground cardamom (optional)
30 gr sifted corn starch
30 gr sifted all purpose flour
a pinch of salt

Raspberry butter cream ingredients:
1 stick of unsalted butter, room temperature
1 cup of confectioner sugar (or more)
3 tbsp tangy raspbery jam (mine has no seeds in it and I mixed it beforehand to make it smooth and clump-less)
Milk


Cooking steps:

1. Get your baking pan ready, grease it and then line it up with a parchment paper. The grease should make the parchement paper stick properly covering the baking pan, set aside
2. Add egg whites and vinegar to the bowl of a stand mixer fitted with whisk attachment and beat on high speed until foamy. Gradually add sugar while continue beating until the egg white mix become thick, fluffy, and tripled the volume. You know your mix is ready when it becomes very stiff that it will not fall out of the bowl when you turn the it upside down, 
3. In another mixing bowl, beat egg yolks until creamy and become pale yellow. Continue mixing while adding oil, milk and vanilla extract. Add sifted corn starch, flour, and freshly ground cardamom gradually. Continue mixing until everything is well incorporated and the batter becomes very smooth and free of clumps, 
4. Take 1/3 of the egg white mix at a time and fold it into the flour mix. Fold gently to incorporate between each addition and scraping from the bottom to catch the hidden egg white clumps, 
5. DO NOT OVER MIX IT, otherwise you will deflate the air bubbles in the beaten egg white mix and your cake will not be fluffy. Stop mixing when you no longer see egg white clumps,
6. Pour the batter evenly (use a spatula to spread the batter if needed) onto the lined baking pan and tap the pan onto the counter to release air bubbles, 
7. Bake right away at 300 F for 30 minutes or until the top is golden,
8. Remove from oven  right away, cover the surface of the cake with a clean, dry linen towel, then flip it gently, 
9. You should now have the cake face down on the linen towel and the parchment paper is still intact, let it cool down
10. Meanwhile, get the raspberry butter cream ready. Using a whisk or electric mixer, mix butter until it softens and creamy, add confectioner sugar and raspberry jam. Continue mixing until it becomes a creamy texture, add milk as needed to thin the mixture. Taste it, add the jam and or the confectioner sugar to your liking, 
11. Once the cake is cool down, gently peel off the parchment paper and spread the butter cream evenly, then gently roll the cake and wrap it with the parchment paper, scrunch each sides (like a candy wrapping paper) to keep it tight. Put the cake away in the fridge for and hour or two, 
12. Before serving, cut each border to make it neat, then dust it with extra confectioner sugar and cut into slices to serve. 

Et voila! This recipe works as a basic fluffy sponge cake. Perfect for shortcake too or even as a base for Christmas Log cake. It is very versatile in terms of flavor, you can add any flavor you want. The cake will be fluffy and yet moist enough that it shall not crack even when you fold it after it gets cool down.