Sift together flour and salt into large bowl. Cut in butter until particles are the size of small peas. Blend together egg yolks, sour cream, 1 teaspoon vanilla, and yeast. Mix well and add to flour mixture. Stir to form dough. Divide dough into 4 parts. Roll out each part on pastry cloth or board which has been sprinkled with sugar (granulated or sifted confectioners' sugar). Roll into 11-inch circle about 1/8 inch thick. Cut into 8 wedges. Spread with filling. Roll each wedge, starting with wide end and rolling to point. Place, pointed side down, on greased baking sheet, curving ends to form crescent shape. Bake in moderate oven at 350° for 25 to 30 minutes, until lightly browned. 

Pecan Filling: Beat egg whites until stiff, straight  peaks form when beater is raised. Add 1 cup sugar, ground nuts, and 1 teaspoon vanilla. Mix until blended.