Put grease proof paper in a large oven tray (30×40 cm). Whisk egg an sugar until white and puffy. Mix flour with baking powder and stir it gently into the batter together with the water. Spread the batter in the oven tray and bake for about 5 minutes in 200°C, ca 5 minutes.

Put a new grease proof paper on your counter top and cover it with sugar. Turn the cake over on the sugary paper and gently remove the paper used for the baking. Spread your berries or jam on the cake and roll it.