Chocolate Swiss Roll (Giraffe Pattern) with Nutella Whipped Cream 长颈鹿蛋糕卷

My first attempt at making swiss roll. Chocolate flavored cake with giraffe pattern. When I told my son I'm going to make a giraffe cake today, he was expecting something like his hippo birthday cake. Not sure if he feels disappointed when he saw this giraffe patterned swiss roll. 
This cake wasn't very successful...Well, the cake tastes really good but technically I was failed in rolling the cake that caused the bottom of the cake cracked. And, I should have tap the baking tray more times to remove the trapped air that caused the 'tiny holes' in my cake. However, I was satisfied with my free hand drawing of the giraffe pattern. Not bad right?
In this blog, I will only archive the chocolate cake recipe, without the methods to roll the cake because I have yet master the skill. I will do more research and try making it again, perhaps with another pattern.


Ingredients:
5 Eggs (cold)
75ml Olive Oil
75ml Water
105g Sugar
105g Top Flour (sifted)
1.5 tbsp Cocoa Powder

Preheat oven 180'C

Methods:

1. Separate egg whites and egg yolks. 

2. Add olive oil, water and half of the sugar to egg yolk. Stir until sugar dissolved. Add sifted flour and stir well to make a smooth batter.

3. In a stand mixer, beat egg whites with medium speed till foamy. Gradually add in the remaining sugar. Beat with high speed till stiff peaks form.

4. Fold the egg whites into batter in 3 batches. 

To draw the giraffe pattern:

5. Put 4 tbsp of batter into a piping bag. Pipe the giraffe pattern on the lined baking tray. Tap the bottom of the baking tray to remove air bubbles. Bake 2 minutes.

6. Mean while, stir in cocoa powder in the remaining batter. 

7. Remove baking tray from the oven. Pour in the chocolate flavored batter. Tap the baking tray again. *Must repeat many times*

I only tap 5-6 times

8. Bake 10 minutes. Place a cooking rack on the cake. Flip the cake upside down. Remove the baking sheet and cover with a new baking sheet. Let it cool on the rack. Fill with Nutella Whipped Cream and roll the cake. 

Mine was not really good because there were too much air bubbles trapped in my cake.