In the mixing bowl of a stand mixer add 4 large eggs, 135g sugar, and oil. Whisk them at the speed of 2 for 4-5 minutes till frothy.
Add cocoa powder, all-purpose flour, baking powder, salt and Mix everything for 2-3 minutes on speed of 2 till well blended.
Now line a baking tray with parchment paper or Silpat.
Pour the cake batter into the thin layer and bake at 180C for 10-12 minutes.
On a flat surface place another parchment paper and sprinkle some cocoa powder over it.
Gently flip the chocolate sponge over the parchment paper while it is still warm. Now roll it very gently into a log-shaped roll and keep it aside.
In the mixing bowl of the stand mixer, add the heavy cream and sugar whip it at a speed of 1 till it forms peaks.
Now gently unfold the chocolate roll. Spread the whipped cream on the cake, this time lift the edge of the parchment paper and roll the cake with filling to form a log/roll.
Refrigerate it for an hour and then cut it into slices as per your preferred thickness. You can make decorate it with a fancy pattern with ganache or chocolate sauce but frankly speaking, I love it as it is with few chopped fruits and a cup of tea or coffee.