Combine the flour, salt and yeast in a large bowl.
Cut in the margarine until mixture resembles coarse crumbs.
Combine the egg yolks, sour cream and 1 teaspoon of the vanilla in a small bowl; mix until smooth.
Add the sour cream mixture to the flour mixture and stir to form a dough.
Beat the egg whites at high speed until stiff peaks form; beat in the sugar and the remaining 1 tablespoon vanilla.
Fold in the pecans.
Divide the dough into 8 equal portions.
Roll each portion into a circle.
Spread pecan filling evenly over each circle to within 1/2 inch of the edge.
Cut each circle into 8 wedges; roll up each wedge from the wide end.
Shape into crescents on a greased baking sheet.
Bake at 375 degrees for 5 to 10 minutes or until beginning to brown.