From a newspaper article called Crossing Delancy: Food and History by Judith Segal. This is what was printed before the recipe "Families which follow the tradition of not eating gebruks should substitute potato flour for the matzoh during passover. A potato kugel may be "parve," containing neither milk nor meat. If it is being prepared specifically for a meat meal, however, rendered chicken fat may replace the vegetable oil. Because poor families could not afford many eggs, the old-fashioned potato kugels were heavier, leaden, due to fewer eggs (a function of cost) and no baking powder. The new, modern, kugels are lighter, creamier, more custardy and souffle-like, the result of using more eggs and adding baking powder."