Preheat your oven to 180°C (350°F).
Grease and line a 15x10-inch jelly roll pan with parchment paper.
In a mixing bowl, beat the eggs and granulated sugar until thick and pale.
Sift together the flour, cocoa powder, and baking powder, then gently fold into the egg mixture.
Pour the batter into the prepared pan, spreading it evenly.
Bake for 12-15 minutes or until the cake springs back when touched.
Once baked, remove from the oven and let it cool for a few minutes.
Carefully roll the warm cake in the parchment paper to form a log shape and let it cool completely.
Whip the heavy cream with powdered sugar and vanilla until stiff peaks form.
Unroll the cake, spread the whipped cream filling, and re-roll. Decorate with melted chocolate and festive toppings.