Preheat your oven to 350°F (175°C) and prepare a baking sheet.
In a mixing bowl, sift together the flour, cocoa powder, baking powder, and salt.
In another bowl, beat the eggs and granulated sugar until pale and fluffy.
Gently fold the dry ingredients into the egg mixture until just combined.
Pour the batter onto the prepared baking sheet, spreading it evenly.
Bake for 12-15 minutes, or until the cake springs back when touched.
Once baked, immediately loosen the edges and invert the cake onto a clean kitchen towel dusted with powdered sugar.
Starting at one end, roll the cake tightly in the towel while it’s still warm.
Let the rolled cake cool completely at room temperature.
In the meantime, whip the heavy cream with powdered sugar until double in volume and soft peaks form.
Carefully unroll the cooled cake and spread the whipped cream evenly over the surface.
Roll the cake back up, without the towel, and refrigerate for at least 30 minutes to set.
Optional: cover with chocolate ganache or icing for a finishing touch.
Slice into pieces and serve chilled for the best flavor and texture.