Start by preheating oven to 220 degree C / 425 degree F. Line a sheet pan or a jelly roll pan or any long tray with parchment paper and grease it well. The parchment paper should come over the sides of the tray.
Take flour, cocoa powder,salt and baking powder in a sieve and sift well. Set aside.
Now separate egg white and egg yolks.
Take egg whites in a clean dry bowl and use a electric beater to whip this till it is frothy and forms soft peaks.
Now take egg yolk and sugar in a bowl and whisk till it gets pale yellow and light.
Now add in the sifter flour mix into the egg yolk and mix well.
Now add in egg white little at a time and fold gently.
Spoon this into the prepared pan and bake for 6 to 8 mins.
Remove it from oven and cool for 2 mins.
Now take a sheet of parchment paper and sprinkle some powdered sugar on top. Invert the swiss roll over the sugar and peel off the parchment paper. Now roll the cake with the parchment papertightly and carefully and set aside to cool completely.
Once the cake is cooled, spread with any frosting as you like, i used my chocolate buttercream.
Roll the cake carefully. Put it in fridge for 30 mins.
Now sprinkle the top with powdered sugar and serve