Preheat your oven to 350°F (175°C) and prepare the baking pan.
In a mixing bowl, beat the eggs and granulated sugar until pale and fluffy.
Add vanilla extract and mix until well combined.
Sift together flour, cocoa powder, baking powder, and salt, then gradually fold into the egg mixture.
Pour the batter into the prepared pan and spread evenly, then bake for about 12-15 minutes.
Once baked, remove from the oven and immediately invert onto a clean kitchen towel dusted with powdered sugar.
Peel off the parchment paper and roll the cake tightly with the towel while it cools.
While the cake cools, whip the heavy cream with powdered sugar until soft peaks form.
Unroll the cooled cake gently and spread the whipped cream over it.
Roll the cake back up carefully and chill for about an hour to set.
Before serving, dust with cocoa powder or garnish with chocolate shavings if desired.