Preheat your oven to 375°F. Line a large rimmed baking sheet with unbleached parchment paper and set it aside.

In a large bowl, place the flour, xanthan gum, cornstarch, 2/3 cup confectioners’ sugar (77 g) and salt, and whisk to combine well. Add the finely chopped nuts and whisk again to combine.

Add the butter and vanilla, and mix until well-combined. I find that pressing down on the butter with the back of a spoon helps to distribute it throughout the dough.

The cookie dough will look somewhat sandy, and will clump in places. Add water by the scant teaspoonful, mixing after each addition, until the dough holds together when scoop or squeezed.

Scoop the dough by the heaping tablespoon (an overfull #70 ice cream scoop is ideal here, but two spoons work well, too). Roll each piece of dough into a round gently between the palms of your hands. Don’t pack the dough; just shape it.

Place granulated sugar in a small mixing bowl. Place each ball of cookie dough in the bowl, and shake it back and forth to coat the dough in sugar. Allow the cookie dough to sit on a flat surface (other than the baking sheet) for 5 to 10 minutes, or until the sugar is less visible, meaning that the dough has begun to absorb it.

Place the balls of dough in the freezer to chill until firm, about 5 to 10 minutes.

Place the remaining 1/3 cup (38 g) confectioners’ sugar in a small bowl. Remove the chilled balls of dough from the freezer, and toss in the sugar a few at a time to coat completely.

Place each of the pieces of dough as it’s coated in confectioners’ sugar onto the prepared baking sheet, leaving about 1 1/2-inches between pieces.

Bake in the center of the oven until the cookies are set in the center and firm to the touch (about 12 minutes). They’ll will be fragile, but shouldn’t be wet.

Remove the baking sheet from the oven and allow to cool completely beforeserving.

These cookies can be stored for at least 3 days in a sealed glass container at room temperature. For longer storage, seal tightly in a freezer-safe container and place in the freezer.