Heat nuts in a dry skillet over medium high heat for 5-8 minutes, shaking pan often until nuts start to turn golden. Remove from skillet and allow to cool completely. Place nuts in mini food processor along with 1 tablespoon of the flour and process until finely chopped. Set aside.
Cream butter and sugar together until smooth and creamy, then add vanilla.
Combine remaining flour, xanthan gum and salt, mixing well. Add into butter mixture in three parts, blending well after each addition.
Stir in the ground nuts then shape dough into a disc and wrap in plastic. Chill for 30 minutes until dough is cold.
Take a teaspoon of dough (the small cookie scoop is the perfect size) and with floured hands roll into a ball. Roll into a 3" log then bend into a crescent shape and place on lined baking pan.
Place baking pan in fridge and chill shaped dough for 15 minutes - this will help them keep their shape as they bake.
Bake at 325°F for 12-15 minutes.
Once done, sprinkle each cookie with a bit of icing sugar (in a small sieve/shaker) then let sit for 5 minutes. This first layer of icing sugar will melt onto the cookie. After 5 minutes liberally sprinkle on more icing sugar as desired.
Allow to cool completely before removing from pan (they will firm up as they cool), then store in a an airtight container.
Notes
If your cookies are spreading out too much in the oven, use an ungreased baking sheet.