SUPER easy - freezable and mailable. I used pecans because that's what I had on hand, but I think walnuts would be wonderful.
In a bowl cream together butter, powdered sugar, and vanilla
Fold in flour, finely chopped nuts, and salt. Mix until just combined well
roll dough into 1" balls and place 1" apart on a cookie sheet lined with parchment.
Bake for 12 minutes until set - but not brown
Let cool AT LEAST 10 minutes on a wire rack, then roll in powdered sugar and let sit. The powdered sugar might get a bit sticky - but it will firm back up if you leave them alone.