Cream butter, brown sugar, and vanilla extract until fluffy.
Combine flour and salt: add to creamed mixture.
Mix well to make a soft dough.
Stir in walnuts.
Pinch off pieces of dough and shape into walnut-size balls.
Bake on ungreased cookie sheets at 375° for 12 to 15 minutes.
Remove from cookie sheets with spatula or pancake turner; cool slightly to prevent cookies from crumbling when handled: then roll in powdered sugar