Preheat oven to 220C and using the cooking spray lightly grease a 22cm x 32cm swiss roll tin and line with greaseproof paper.
In a small glass Pyrex bowl sift the flour, baking powder and cocoa powder together.
In a large mixing bowl whisk the eggs and sugar together until thick and creamy. Use an electric whisk if you have one.
Using a spatula, gently fold the flour and cocoa mixture into the whisked mixture. Make sure there are no lumps in the mixture.
Pour the mixture into the swiss roll tin and smooth over the top.
Bake in the oven for 8 - 10 minutes until a sponge is formed. Make the filling.
Allow the cake to cool slightly then turn the cake out onto another sheet of greaseproof paper which has been lightly sprinkled evenly with some caster sugar.
Peel off the backing greaseproof paper and trim the edges of the sponge.
About 2.5cm from the bottom edge of the sponge score a line using a sharp knife but be careful not to cut all the way through.
Fold over the scored line and use the paper to gently roll up the sponge. Then unroll it gently.
Spread half of the filling evenly over the sponge and gently re-roll it. Then pour the rest of the filling over the top. Place in fridge for one hour.