Preheat the oven to 350°F. Prepare a baking sheet size 15x11 inch, then line it with parchment paper.

Beat the egg yolks with a hand whisker until they are well mixed. Add oil and milk. Stir well.

Sift the flour and cocoa powder, then pour into the egg yolk mixture. Stir until the batter looks smooth.

Beat the egg whites with an electric mixer until foamy. Add sugar in 3 stages while continuing to beat. Beat the egg whites until firm peak.

Spoon the egg white meringue into the egg yolk mixture in 3 stages. Fold the batter in with a spatula until evenly mixed.

Pour the batter in the pan. Bake until cooked for about 15 minutes. Do a skewer test. When the skewer comes out clean, it means the cake is done.

Once cooked, remove the cake from the oven. Turn the cake over the cooling rack. Remove the parchment paper and then immediately rolled (cake is still in hot condition) with parchment paper.

Allow the cake to cool completely. Open the cake roll, then spread with buttercream (I use buttercream with the recipe 👉 # pib_swissmeringue).

Roll the cake back. Wrap tightly with parchment paper, keep it in the refrigerator for at least 1 hour so that the cake sets and then slice it.