Mix butter at room temperature and sugar with yellow yolk of the eggs and add some vanilla essence. Then continue beating this mixture till sugar in it becomes fully soluble. Note with care that butter from refrigerator should keep out for 2/3 hours before use to get the same at room temperature. Now mix baking powder with flour suitably and add it to the mixture of yolk, sugar & butter. Intermix all these items properly by shaking through a spatula. Add half of the foamy white portion of eggs and mix thoroughly. Then add the remaining half of the same too and intermix through cut and fold process so that no lump of flour exists. It is wise to sift the flour by a sieve to drop out probable impurities and at the same time to get somewhat aerated too.