Preheat the Oven: Preheat your oven to 350°F (175°C). Line a 10×15 inch jelly roll pan with parchment paper.

Prepare the Batter: Sift together flour, cocoa powder, and baking powder in a bowl. In a separate bowl, whip the egg yolks and half of the sugar until thick and pale. In another bowl, whip the egg whites until soft peaks form, then gradually add the remaining sugar and beat until stiff peaks form. Gently fold the egg yolk mixture into the flour mixture. Then, carefully fold in the egg whites, ensuring not to deflate them.

Bake the Cake: Spread the batter evenly in the prepared pan. Bake for 10-12 minutes, until the cake springs back when lightly touched.

Roll the Cake: While the cake is warm, dust a clean kitchen towel with powdered sugar. Turn the cake onto the towel and peel off the parchment paper. Roll the cake, with the towel inside, starting from one of the short ends. Allow it to cool completely.

Prepare the Filling: Whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form.

Fill and Roll the Cake: Unroll the cooled cake and spread the whipped cream evenly. Roll it back up, this time without the towel. Wrap the rolled cake and refrigerate for about an hour.

Coat the Cake: Coat the Swiss roll with chocolate ganache or frosting.

Garnish and Serve: Decorate with fresh berries or your choice of garnish. Slice and serve.