• Preheat the oven to 160°C. Line a 28x28 cm baking pan with parchment paper or a non-stick baking mat, ensuring it fits well with the edges slightly overhanging for easy removal after baking.
• Separate the eggs. Place the egg whites and yolks in two clean bowls. Put the egg whites in the freezer for 15 minutes to make them easier to whip and more stable.

Make the egg yolk batter:

• In a bowl, combine 50g milk and 50g corn oil, and whisk until emulsified (you should see a smooth, uniform mixture with no oil droplets).
• Sift in 60g cake flour and fold gently with a spatula in a "Z" shape until there are no dry flour bits and the batter is smooth.
• Add 5 egg yolks and stir until the batter is smooth.
• If you're making Earl Grey flavor, add 4g Earl Grey tea powder to the batter and mix well. Skip this step if making a plain roll.

Whip the egg whites:

• Take the egg whites from the freezer and add 3-5 drops of lemon juice. Whip with an electric mixer on low speed until large bubbles form.
• Gradually add 50g fine sugar in three stages. Continue whipping, increasing speed with each addition (low, medium, then high). Stop once the meringue forms soft peaks and can hold its shape without being too stiff.

Combine the batters:

• Fold one-third of the meringue into the egg yolk mixture, mixing gently with a spatula from the bottom up.
• Pour the mixed batter back into the remaining meringue, and continue to fold gently with a spatula using the same technique, until the batter has a consistent color and smooth, even texture.

Bake the cake:

• Pour the batter into the prepared baking pan and smooth the top with a spatula.
• Tap the pan lightly on the counter to release large air bubbles.
• Bake in the preheated oven for 25 minutes at 160°C. Avoid opening the oven door during baking to ensure the cake rises properly.

Prepare the filling:

• While the cake bakes, whip 180g whipping cream and 15g fine sugar in a clean bowl with an electric mixer. Whip on low speed, then gradually increase to medium until stiff peaks form.
• Chill the whipped cream in the fridge until ready to use.

Assemble the cake:

• Once the cake is done, remove it from the oven and allow it to cool on a wire rack.
• When cool, carefully invert the cake onto a new piece of parchment paper. Peel off the top layer of parchment.
• Spread the chilled whipped cream evenly on the cake, leaving a bit less on the edges.
• Use a rolling pin to slowly roll the cake from one end. As you roll, make sure to roll tightly to avoid any gaps. Once rolled, gently press both ends with your hands to make the Swiss roll more compact.

Chill and cut:

• Place the rolled cake in the fridge for 30 minutes to set. This will make it easier to cut.
• Once chilled, remove the roll and slice it into even pieces using a sharp knife. Now you can enjoy your delicious Swiss roll!