Work butter, flour and salt as for pie dough. Dissolve yeast in 1/4 cup lukewarm water. Put yeast mixture in bowl with whole egg, 3 yolks, sour cream and beat slightly. Add to flour and mix together. Knead until smooth. Cover with wet cloth and refrigerate. Roll very thin in granulated sugar. Cut in 3 inch squares, fill center with fruit mixtures, fold and brush with egg white. Bake at 375 degrees for 20-25 minutes. Do not store in an air tight tin. These stay crisp and delicious for about 10 days.{$7e}(Original recipe for 12)
