Make the egg yolk batter. Mix 40g of oil and 40g of milk until emulsified.

Sift 40g of low-gluten flour into the oil mixture and whisk in a Z-shaped motion until well combined. Sifting is crucial to prevent clumps, combine smoothly, and avoid overmixing. You don't want to overmix the batter since this will remove the air bubbles needed for a light and airy batter.

Separate the egg yolks from the white. Add 4 egg yolks to the batter and whisk in a Z-shaped motion.

Make the egg white batter. In a separate bowl, beat 4 egg whites using an electric whisk. Although you can use a manual hand whisk, it will take a longer time and more effort to form a frothy egg white batter. So, I recommend an electric whisk to do this step faster with less effort.

Gradually add 40g of sugar in three parts: when large bubbles form, when small bubbles appear, and when the mixture forms medium peaks. Do not stop beating until you form a frothy mixture. Medium peaks can hold their shape, but you can see the tip curls when you lift the whisk.

Combine the egg yolk and egg white mixtures. Combine half of the egg white batter with the egg yolk batter. Use a silicone spatula to gently mix and fold until well incorporated.

Then, pour this mixture into the remaining egg white batter and fold until fully combined. The batter should become light and fluffy. You want to do this step slowly to avoid overmixing and removing air, which can cause the mixture to lose volume.

Pour the batter onto a baking tray lined with parchment paper. Use a dough cutter or knife to spread the mixture evenly and flatten the top. Set aside.

In the meantime, make the black tea roll egg yolk batter. Mix 40g of oil and 40g of milk. Sift 40g of low-gluten flour into the oil mixture.

Add 5g of black tea leaves and whisk in a Z-shaped motion until well combined.

Add 4 egg yolks to the batter and whisk in a Z-shaped motion.

Make the black tea roll egg white batter. Beat 4 egg whites using an electric whisk. Gradually add 40g of sugar in three increments.

Combine the black tea egg yolk and egg white mixtures. Mix and fold half of the egg white batter with the egg yolk batter. Combine the remaining amount of egg white batter and fold until fully combined.

Pour the black tea batter onto a baking tray lined with parchment paper. Spread the mixture evenly and flatten the top.

Preheat the oven to 150°C.

Bake the classic Swiss roll flavor for about 40 minutes. You know the cake is ready when it is springy and returns to its shape when pressed. Avoid overbaking the cake. Otherwise, the cake will crack and become too dry for rolling.

Bake the black tea Swiss roll flavor for about 40 minutes.

Take it out from the oven and turn it over to a flat surface lined with parchment paper.

Replace the old parchment paper with a clean one. This should cover both sides of the cake with parchment paper.

Flip it again to the other side and remove the parchment paper on top. The side facing you should be the top baked side, which is usually the one with the uneven side. The uneven side is where you should spread the cream.

Prepare the whipped cream filling by whisking together 200g of cream and 20g of sugar until stiff peaks form.

Make a second batch of the cream for the black tea rolls with another mix of 200g of cream and 20g of sugar. Set aside.

Spread the whipped cream evenly over the surface of the cake.

Lift the cake using the edges of the parchment paper and gently let it roll into a spiral cake. When fully rolled, you can use a rolling pin at the end to compress the roll a bit.

Cut the cake into even slices and serve. Rolling Tip: Flip the cake while it is still warm. Roll it (without the cream) and let it cool in this rolled shape. Afterward, unroll it, spread the cream, and roll it again. In this way, it prevents the cake from cracking. If you let the flat cake cool too much before rolling, the risk of cracking is higher. If there are cracks, that's okay! Just cover it with cream to make it look nicer.

Repeat steps 1 to 3 for the black tea Swiss roll.

Enjoy the soft, moist cake with smooth, sweet cream and a hint of black tea flavor!