A rather challenging but fun bake. Please have all ingredients and equipment ready before starting, because you will also need to act quickly through all the steps, and multi-task. Also, a must to follow the tray dimension. I used a smaller tray and ended with a thicker and shorter sponge, which cracked inside.

Baked on 14 July 2018:

Tried a flower variation with a drop of red coloring to the stripe batter. Also changed to a Nutella cream cheese filling which tastes awesome ( mix about 2 tbsp each of Nutella and spreadable cream cheese).

Recipe

Yolk batter

• 3 egg yolks
• 30g caster sugar
• 60g milk
• 40g cooking oil
• 1/2 tsp vanilla extract
• 70g cake flour
• 10g cocoa powder

Egg White Meringue

• 4 egg whites
• 1/4 tsp cream of tartar
• 35g caster sugar

Stripe batter

• 2g cake flour

Filling

• Nutella (or you can add spreadable cream cheese to the Nutella, about 2 tbsp each.)

1. Prepare 28cm by 28cm baking tray. Line all sides with baking paper, use a little oil to help the paper stick to the side of the tray so that it would not distort the cake shape.

2. Cream egg yolks with sugar till light and fluffy. Add in oil slowly while whisking till a thick paste like mayonnaise forms. Next add in milk and mix till combined.

3. Add in sifted cake flour and fold gently with hand whisk till all flour disappears. Small lumps are fine. Set aside.

4. Prepare meringue. Beat egg whites till large bubbles, add cream of tartar. Continue beating and add sugar in 3 batches. Whisk till soft peak (hooks form like below). Place into refrigerator to prevent meringue deflating.

5. Prepare stripe batter. Spoon out 1 heap tbsp of egg batter, add 2g of cake flour and mix well. Add approximately 3 tbsp of meringue and mix well with a spoon. Spoon into piping bag and cut a small tip. Pipe pattern onto baking paper in the baking tray.

6. Preheat oven to 170deg C. Bake stripes for 1.5min or 90 seconds. There is no need to cook through, we just need a film layer. Hence cooked and uncooked stripes look almost identical.

7. Add sifted cocoa to egg yolk batter and fold till combined. Add 1/3 of meringue to yolk batter and mix with hand whisk. Pour yolk batter back into remaining meringue and fold gently till no white streaks are seen.

Pour batter into tray over stripes at a height slowly to release air bubbles. Tap baking tray on counter 3 times to release more bubbles.

8. Bake at 170 deg C for 12-15 mins. The sponge should spring back when pressed gently.

9. When done, place the sponge cake with the stripes facing up onto a cooling net. Gently remove the baking paper, but leave it on top to reduce moisture lost while the cake cools. You can see the beautiful pattern formed here.

10. When cake has cooled slightly, turn it around and place it on another clean baking paper. Make shallow slits as shown. Spread Nutella onto the cake.

11. With the help of the bottom paper, roll up the cake. And then wrap tightly with the baking paper. Place into the fridge for 1 hour to set the cake. Slice and enjoy.