Carefully separate the egg whites and yolks, ensuring that the container for the egg whites is completely free of oil and water. Place the egg whites in the freezer for about 20 minutes.

In a large bowl, pour in 50g corn oil and 50g milk. Use a hand whisk or spatula to mix thoroughly until emulsified, with the liquid becoming uniform and free of any separation of oil and water.

Sift in 60g cake flour into the emulsified liquid. Gently stir using a “1” or “Z” motion with a spatula until there are no dry flour clumps in the batter.

Add the 5 egg yolks and continue stirring with the same method, making the batter smoother.

Take the egg whites from the freezer and add a few drops of lemon juice. Begin whipping the egg whites at medium speed. When large bubbles form,add one-third of the fine sugar (about 17g).

Continue whipping until the foam becomes finer, then add the second portion of fine sugar (about 17g).

When visible peaks begin to form, add the final third of fine sugar (about 16g), and reduce the mixer speed to low. Whip until soft peaks form, where the egg whites hold a large hook-like shape when the whisk is lifted.

Take about 1/3 of the whipped egg whites and add them to the egg yolk batter. Gently fold with a spatula until well combined. Then, pour the mixed batter back into the remaining egg whites and continue folding until fully incorporated.

Take about 30g of the prepared cake batter and place it in a small bowl. Add 2g cocoa powder and mix well.

Fill a piping bag with the cocoa batter.

Line a 28×28 cm baking pan with parchment paper. Pour the regular cake batter into the pan and gently shake to level the surface, or use a spatula to smooth it out. Tap the pan twice to release large air bubbles.

Pipe several vertical lines on top of the batter. Then, using a bamboo skewer, trace a figure-eight shape along the cocoa lines to create a beautiful swirl pattern.

Preheat the oven to 160°C. Once preheated, place the pan into the oven and bake for 25 minutes at 160°C.

Note: Oven temperatures may vary, so adjust time and temperature based on your oven's performance.

After baking, remove the cake from the oven and let it cool on a wire rack. After the cake has completely cooled, place a new sheet of parchment paper on top, then invert the cake. Carefully peel off the original parchment paper, making sure the cake retains its shape.

On the cooled cake, make a vertical cut near your body, then make a diagonal cut further from you.

For the filling, place 200g of heavy cream into a container, add 16g of fine sugar, and whip until it holds its shape.

Spread a generous layer of whipped cream on the third of the cake closest to you, then arrange the strawberries on top. Add more whipped cream on top of the strawberries.

Using a rolling pin, slowly roll the cake up. While rolling, gently pull the parchment paper to ensure the roll is tight.

Once rolled, let the cake set for a while before cutting it into your desired portion sizes.