Separate egg yolks and whites; set each aside. Sprinkle
yeast and 1 teaspoon sugar over warm water; let stand
5 - 10 minutes, or until yeast is softened. Place flour and
salt in bowl, cut in butter until mixture resembles coarse
meal. Blend in egg yolks and yeast mixture. Mix until a
smooth ball is formed. Beat egg whites in small bowl until
stiff peaks form; gradually add the 1/2 cup sugar. Fold in
vanilla. Divide dough in half. Roll out one half on lightly
floured surface into a 13 x 9" rectangle. Spread with half
of egg white mixture; sprinkle with half of the nuts. Roll up
as for jelly roll. Place on greased baking sheet. Make a 1/2"
deep cut lengthwise. Repeat with remaining dough and
ingredients. Do not let rise, but bake immediately at 375F
for 22 minutes. While warm, sprinkle with powdered sugar.
Cool thoroughly before slicing.