For the dough, mix yeast with 1 teaspoon sugar in lukewarm water; set aside until bubbly. Cut 1 pound of margarine into flour as for pie dough. Add yeast mixture, egg yolks, sour cream and 1 teaspoon vanilla. Mix well. Divide dough into 4 parts; wrap in waxed paper and refrigerate overnight. 

For nut filling, mix together walnuts, 1 cup sugar, 1/4 cup margarine and 1 teaspoon vanilla. Fold beaten egg whites into the mixture.

Roll out refrigerated dough on floured surface 1/8 inch thick. Spread with nut filling and roll up like a jelly roll. Place on lightly greased baking sheet; let rise 30 minutes. Bake at 350° for 30 to 35 minutes.