To make dough: Place flour in large bowl. With pastry blender, cut in butter until mixture resembles coarse crumbs. Add egg yolks and sour cream; stir until combined.

Turn out on lightly floured surface and knead until dough is smooth and can be shaped into ball. If too sticky, knead in more flour. (Dough can be refrigerated until ready to use.)

Make filling: In medium bowl combine nuts, sugar, milk, and almond extract; blend well. Preheat oven to 400 degrees. Grease cookie sheets.

To shake Kifli: On lightly floured surface, roll out a quarter of dough at a time to measure 16x12x1/8 inches. With pastry wheel, cut into 2-inch squares. Place generous 1/2 teaspoon filling in center of each square, then bring 2 opposite corners, overlapping, over filling; pinch edges together to seal. Place on cookie sheets. Brush lightly with egg whites. Bake 10-12 minutes or until golden. Remove and roll in confectioners sugar. Let cool. Makes 16 dozen.