Separate the whites from the yolks. Sift flour, add baking powder, stir slightly. Put butter at room temperature, a pinch of salt, 50 g of sugar, vanillin in a deep bowl, mix with a blender (mixer) until smooth. Add one yolk one by one and mix with a blender (mixer) until smooth. Gradually, in a couple of tablespoons, add flour and begin to knead the dough in a bowl with a spatula. It turns out a homogeneous non-sticky dough that does not crumble.