In electric mixer beat egg whites thoroughly, then add yolks.
Crumble cream cheese and feta cheese into the size of marbles and drop into well-beaten eggs.
Cut each sheet of filo across the width, not the length, into 6 strips each about 2 inches wide.
Place the filo under a slightly damp towel to keep it from drying out until you are ready to use it.
Place 1 strip of filo on the working board perpendicular to the table edge and brush it with the butter and margarine mixture.
Place a second strip over the first and brush with butter mixture.
Place 1 teaspoon of the filling on the end of the pastry strips nearest you and fold the corner over the filling to make a triangle.
Continue folding from side to side in the form of a triangle (like folding a flag) until the end of the strip is reached.
Brush folded tiropita with butter and margarine mixture to seal it.
Place the uncooked tiropites in a foil-lined box with a sheet of foil between each layer of tiropites.
These may be kept frozen until about 25 minutes before you are ready to use them.
Place the number desired on a cookie sheet (straight from the freezer) and cook at 350° until they puff up, then reduce heat to 325° and cook until golden brown, 20-25 minutes.