Stir walnuts, oats, brown sugar, cocoa and flour in a medium bowl, mix well and set aside. Preheat oven to 375°F, then reduce to 325°F. Combine egg whites, vanilla and salt in a dry mixing bowl. Beat with electric mixer on high until soft peaks form. Gradually add sugar and continue beating on high until stiff peaks form. Gradually fold in dry mixture with rubber spatula. Drop level tbsps of dough onto cookie sheet, then bake 15 to 17 minutes, or until tops of cookies no longer look wet. Store in loosely covered container. Makes 3 dozen cookies.