Cotton Sponge Roll 黃金蛋糕捲

Wow, the whole building was just shaken by a 4.6 earth tremor as I’m finalizing this post (Friday night, 6th Mar), felt like I’m on the sea…

This is the third variation on the Japanese Cottonsoft Sponge Cake recipe which I originally adapted from ‘Japanese Cotton Sponge Cake’ recipe by Alex Goh. Last time I changed it into a Vanilla Cotton Chiffon Cake. This time it is a sponge roll!
After the problem of sticky crust the first time I made it as a sheet cake, I adjusted the recipe slightly this time so the cake is not as fragile and I also baked it at a higher temperature to make sure the crust was dry. The result was fantastic and I even attempted for the first time the zig-zag pattern for the crust – have been wanting to do this for ages.
The only problem I had was my Cocoa Butter Cream. As I had my butter chilled, I had to soften it in the microwave. Being impatient, I over heated the butter and it melted. I had no choice but to continue and add the sugar to the melted butter and then stir in the cocoa powder (since the melted butter was already warm, so I did not dissolve it in hot water), then chilled the mixture in the refrigerator until it firmed up. The preparation for the butter cream included below was what I intended to do in the first place if I had not make the silly mistake.
One other thing was that since I had never done the zig-zag pattern before, I think I had spaced the lines too far apart this time. Next time need to space the lines closer to get a better zig-zag pattern after rolling up.

Makes one 30cm x 25cm sheet cake, roll up into approx. 20cm long roll

[Ingredients]
Japanese Cotton Sponge:
50g butter
55g plain flour
40ml milk
1/2 teaspoon vanilla extract
1 whole egg
3 egg yolks
3 egg whites
1/4 teaspoon salt
80g caster sugar

1 teaspoon cocoa powder
1 teaspoon hot water

Cocoa Butter Cream:
100g butter, softened
50g pure icing sugar
1 teaspoon cocoa powder
1 teaspoon hot water
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[Preparation]
1. Preheat oven to 180°C. Grease a 30cm x 25cm Swiss roll tin and line the base with baking paper.
2. Melt butter over gentle heat and bring to just simmering. Remove from heat and add flour all at once, whisk quickly to form a thick roux. Add milk and vanilla, whisk to combine.
3. Add whole egg and whisk until smooth. Add egg yolk one at a time and whisk in well after each addition. Transfer the mixture to a large mixing bowl, set aside.
4. In another mixing bowl, beat egg whites and salt until foamy. Gradually add sugar, one tablespoon at a time, and beat until just under stiff peaks stage.
5. Fold 1/3 of the egg white mixture into the yolk mixture. Repeat two more times with the remaining egg white mixture.
6. Dissolve the cocoa powder in hot water in a small mixing bowl. Remove two tablespoons (or three tablespoons for closer zig-zag lines) of the sponge batter and mix into the cocoa mixture. Transfer the cocoa mixture to a small plastic freezer bag and make a small cut in one corner for piping.
7. Pour the remaining sponge batter into the prepared tin. Smooth the surface and give the tin a gentle tap on the bench to settle the batter. Pipe parallel lines of the cocoa mixture on top of the sponge batter. Then use a skewer to draw across the cocoa lines to form pattern.

8. Bake for 15 minutes at 180°C, turn heat down to 170°C and bake a further 5 minutes, or until the cake feels springy when touched lightly.
9. Remove from oven and loosen the sides of the cake from the tin. Turn out onto a tea towel immediately. Remove lining paper and let cake cool completely this way, about 20-30 minutes or until room temperature. Do not let it cool too long or the cake will lose too much moisture and crack when rolling up.
10. Cut away the hard edges from the cake. Spread Cocoa Butter Cream onto the cake. Roll up from the short side; roll as tightly as possible. A good way to roll up the cake is by placing a rolling pin at the end where you are going to start rolling (with the sheet cake still sitting on the tea towel). Fold the end of the tea towel over the rolling pin to wrap it up. Then start rolling the rolling pin forward (as you roll more of the tea towel will wrap over the pin), at the same time start rolling up the cake in front of the rolling pin. Keep rolling the pin forward until the cake if fully rolled up. Then release the rolling pin from the tea towel and now wrap the tea towel over the cake roll and leave it until the cake roll is stable before cutting and serving.

Cocoa Butter Cream:
Dissolve the cocoa powder in hot water. Cream butter and sugar until light and fluffy. Mix in cocoa mixture.

Taste: Spongy, moist and soft cake roll with cocoa butter cream filling
Consume: Best within 2-3 days
Storage: Store in airtight container in the refrigerator
Recipe References: ‘Japanese Cotton Sponge Cake’ by Alex Goh