Step 1

Preheat your oven to 325°F. Line rimmed baking sheets with unbleached parchment paper and set them aside.

Step 2

In a large bowl, place the flour, xanthan gum, cocoa powder, sugar and salt, and whisk to combine well.

Step 3

Add the butter, egg and vanilla, and mix until the ingredients are mostly combined.

Step 4

With clean hands, knead the dough until smooth. If necessary to bring all of the dough together, add 1 teaspoonful of lukewarm water and knead it in.

Step 5

Divide the dough into two equal parts, and roll each out between two sheets of unbleached parchment paper until the dough is 1/8 inch thick (the thickness of a nickel), no thinner.

Step 6

Pull back the top sheet of parchment paper on one piece of dough.

Step 7

With a round 2 1/4-inch cookie cutter, cut out rounds as close to one another as possible. Remove the surrounding dough, and set it aside.

Step 8

Transfer the rounds to the prepared baking sheets, and place them about 1/2-inch apart (they will not spread during baking).

Step 9

Gather the scraps, roll them out again, and cut more rounds.

Step 10

Repeat with the second piece of dough.

Step 11

Place the baking sheets, one at a time, in the center of the preheated oven and bake, rotating once during baking, for 8 minutes or until the cookies spring back when pressed lightly in the center.

Step 12

Remove the baking sheet from the oven, and allow to cool on the baking sheet until firm.

Step 13

Transfer to a wire rack to cool completely.