Place 3 cups of flour in a large bowl; 3 cups on a large board. In a large wooden bowl, mix the butter, shortening, 1 cup of flour, 2 teaspoons sugar. Use a blender to cut it into small pieces, then crumble the flour and the butter gently with your hands until all flour is mixed with butter. It looks lumpy. Then place in refrigerator.
In an enamel pan, crumble the yeast into the warm milk and 1 teaspoon sugar. Mix 1 cup of flour to this mixture with a spoon. Set aside to rise in warm place - about 15 minutes.
Return to the 3 cups of flour on the board. Add 2 tablespoons sugar, make a well and add the sour cream in this center hole. Drop the egg yolks into the well and mix with spoon. Pour on the yeast mixture. Mix and knead until the yeast and other ingredients are well blended. Work it very hard until it is elastic. Clean hands with flour into the dough and keep working until the dough forms a ball and turns bubbly, no longer sticks to the hands, and can be handled more easily.
Also it turns firm under the hands and can be moved off the board. Now flour board and places ball of dough on board, roll out, fold over, sprinkle with flour and roll again, making sure dough doesn't stick to the board. Check under the dough frequently to make sure it isn't sticking. Roll out as large as possible.
Take the bowl from the refrigerator and add that dough onto the rolled dough. Press down firmly. Bottom dough should be bubbly. Fold over half, then, fold the half into a fourth and put on floured board. Roll out again, rolling the same way you folded it. Roll gently. Do not press down on rolling pin. Keep rolling gently as wide as possible. Now fold a second time in the same direction as the first. Press down on each section, fold over the opposite direction. To fold: Put left end in to center, then right end into center, then upper end and then lower end into center. For the third and final time, just fold, then roll out on about one half of the board. Roll up the dough tightly like a jelly roll. Press ends together on side and middle. Give three patches across the top. With sharp knife, cut 2-inch slices across like a jelly roll. Press each slice down. press firmly. Wrap each patty in waxed paper and refrigerate or freeze for later use.
To prepare: Remove one roll of dough at a time from the refrigerator. Flour a board and roll dough out, but not too thin, to about the diameter of a large frying pan. Cut into squares or triangles. Cut-away scraps can be pressed together and wrapped in waxed paper and returned to the refrigerator for a later large ball of dough.
The dough should make about 15 squares or 30 triangles. On each square, put a teaspoonful of cheese in the center, pinch two opposite corners together, then the sides as though you were making a nest. Next pull up the other two corners and pinch together and squeeze sides. Place on lightly greased baking or cookie sheet about ½ inch apart. Mix the egg white with a little water and brush over entire cookies before baking. Bake at 350 degrees F. until golden brown.
The dough may be frozen for later use.
Yield: 42 pieces out of 2 - ½ rolls; 38 pieces out of second half.