Heat oven to 400. Mix butter, 1/2 cup powdered sugar, and the vanilla. Mix in flour, salt, and nuts unjtil dough holds together. Shape dough into 1-inch balls. Place about 1 inch apart on ungreased cookie sheet. Bake until set, but not brown - about 10 to 12 minutes. Roll in powdered sugar while warm. Let cool. Roll in powdered sugar again.