The amount of a baking tray left and right.
Butter and sugar powder to whiten, add the egg solution twice, each time for about two minutes, until it is even.
Add flour and cocoa powder and stir until the dry powder is added. Stir well.
The cling film can be wrapped in a round square shape. Place in a freezer to freeze enough to cut into 5 mm thick sheets. 190 degrees and 12 minutes or so, be careful not to color too deep. (Adjust the temperature according to the temper of your own oven.)