1/2 lb. unsalted butter
1/2 lb. cream cheese
2 c. flour
Cut butter and cheese into flour. With hands, press dough into firm ball. Wrap dough in wax paper or foil. Place in freezer to chill.
~ 3 lb. potatoes
~ 1 1/2 lb. onions
(or more or less potatoes and onions in similar proportions)
~ 1/4 lb. butter
1 or 2 eggs
Dice onions and cook in butter until soft and yellow. Peel and cook potatoes until soft. Mash potatoes, add cooked onions, 1-2 eggs, and salt and pepper to taste.
Cut off small piece of dough. Roll into thin rectangle on well-floured board, adding more flour if necessary to keep from sticking. Place potatoes along long edge and roll up as if for jelly roll. Slice into knishes - continue until dough and potatoes are used up. (Cool potatoes slightly before placing on dough.)
Bake at 425 F until brown (~25 minutes). Can be frozen instead.