Mix butter, sugar, and vanilla thoroughly. Stir flour and salt together; blend in. Mix in nuts. Chill dough. Heat oven to 400. Roll dough in 1" balls. Place on ungreased baking sheet. (Cookies do not spread.) Bake 10 to 12 min., or until set but not brown. While still warm, roll in confectioners' sugar. Cool. Roll in sugar again. Makes about 4 dozen.