Add half a teaspoon of baking powder to the flour (actually, ammonium bicarbonate is in the original, but I do not know where to get it, and baking powder in such a small amount is needed to cope with raisins). Sift once or twice, check if all the sugar has dissolved in our butter-egg mixture (rub a drop between your fingers, if sugar is not felt, everything is ready), spoon all the flour into the mixture. The mass increases in volume, becomes very tender, oily, airy.