In the bowl of a food processor, combine the coconut sugar, milk, stevia, vanilla, coconut oil, and flax until the sugar is dissolved. Add the cocoa powder, flour, baking powder, xanthan gum, and salt. Pulse to incorporate the flour, then process until it comes together in a soft dough. Turn the dough onto a piece of plastic wrap, form into a disk, and refrigerate until firm, at least 30 minutes to an hour.

Preheat oven to 375°F. Line a baking sheet with parchment paper.

Dust a clean, flat surface with a thin layer of flour. Roll out the dough to about ¼-inch thickness. Cut into desired shapes.

Place cookies on the baking sheet. Bake 10-12 minutes, until dry on top and browned on the edges. Allow to cool 5 minutes before transferring to a rack to cool completely. May be frozen.