Preheat your oven to 200 Degrees Celsius and prepare a swiss roll tray with an extra large piece of baking paper. You want to make sure you've got a good almost 10cm over hang on each end (this will be vital when it comes to remove it and rolling your roll later). If you don't have a swiss roll tray an extra large baking tray that's 35x25cm will work.
In a large bowl place the eggs and using hand beaters, beat until fluffy and light.
Add the caster sugar a couple of tablespoons at a time, beating all the time. Almost think of it like creating a pavlova, only we're not chasing stiff peaks here.
Sift over flour and cocoa powder and fold through very gently.
Pour into your prepared tin and smooth all the way out into each corner. Bake for 8-10 minutes. It will rise quite a bit and then decrease a little once it starts cooling, don't stress! It will make it easier to roll.
Now working whilst it's still hot, lay a second piece of baking paper out on your counter just larger than your tin and sprinkle with extra caster sugar. Using the hanging edges of the hot tin, carefully remove your swiss roll and turn it upside down onto the sugar. Peel back the extra baking paper and discard.
Starting at one of the short ends, tuck the baking paper over the edge and gently start rolling your roll. Be sure to keep it quite loose, you want to leave enough room for cream and not put too much pressure on the roll so that it cracks.
Now leave rolled up on a wire rack to cool fully.
Place the whipped cream and icing sugar into a bowl and whip until stiff peaks.
Once the roll has cooled fully, slowly and gently unroll it. (Don't force it flat, otherwise it may crack). Fill with cream and gently roll back up again, be sure to take the baking paper off this time and rest it so that the edge sits underneath.
Can be cut and enjoyed immediately! Otherwise wrap tightly in cling wrap and place into the fridge. Best eaten with 2 days, not that that will be a problem of course!