In a large bowl, combine butter, powdered sugar, vanilla and salt on low speed of mixer about 1 minute until well blended.
Gradually add flour at low speed until just combined.
Stir in nuts.
Roll dough into 1-inch balls.
Place about 1 inch apart on ungreased cookie sheet.
Bake at 350° for 8 to 10 minutes until firm to the touch but not brown (do not overbake).
While warm, roll in powdered sugar.
Cool, roll again in powdered sugar before serving.