Drain potatoes; mix with onion.
Beat in eggs.
Stir in a mixture of matzo meal, baking powder, salt, and pepper.
Blend in chicken fat or butter.
Turn into a greased 9 inch pie pan or a shallow casserole.
Dot with additional chicken fat or butter.
Bake at 350°F about 1 hour, or until top is crisp and browned.