Step 1

In a large bowl, cream butter and confectioners' sugar until light and fluffy, 5-7 minutes. Beat in vanilla. Combine the potato starch, cornstarch, xanthan gum and salt; gradually add to creamed mixture and mix well. Stir in walnuts. Cover and refrigerate for 1 hour or until easy to handle.

Step 2

Shape into 1-in. balls; place 2 in. apart on ungreased baking sheets. Bake at 400° for 9-11 minutes or until set. Cool on pans for 2 minutes before removing to wire racks.

Step 3

Roll warm cookies in confectioners' sugar. Cool completely on wire racks. Reroll in confectioners' sugar.