Start by lining a small rimmed baking sheet with wax paper and set it aside.
Place the flour blend, xantham gum, cocoa powder, baking soda, salt, and granulated sugar in a bowl and begin to whisk.
Add the brown sugar and continue to whisk till there are no traces of lumps left.
Create a well in the center of the dry ingredients and add the butter, vanilla, and 1 tablespoon of milk. Mix after adding each ingredient.
It's time to knead the dough. Do this with your hands and add more milk as much as you need for the dough to stick together without crumbling.
After this, break off small pieces of brownie dough and roll tightly into balls about 1/2-inch in diameter.
Place the rolled balls on the prepared baking sheet in a single layer, and place in the freezer until it becomes firm. Leave for 10 minutes.
Once it becomes firm, remove the cookie dough from the freezer and cut each ball in half
Return to the freezer.