Preheat the oven at 160 degrees Celsius.
Butter an oven form 20 cm x 20 cm.
Mix the egg whites to a hard foam.
Mix the egg yellows and the sugar until it becomes pale yellow in color. About 1-2 minutes.
Add the melted margarine and the vanilla extract with the egg yellow and sugar mixture. Mix for about 1 minute.
Add the flour and mix well.
Heat up the milk to lukewarm and add it in the batter. Mix well.
Fold in the egg white foam gently with a spatula. Don’t worry it will be lumpy on the surface.
Pour the batter in the oven form and place in the middle of the oven for 50 minutes. The surface should be brown in color when the cake is ready. The cake should stop jiggle, that means its ready.
Take out the cake and let it cool for 10 minutes.
Place it on a plate and let it cool down.
Sprinkle the icing sugar and cut in small squares before the serving.