Preheat oven to 400 F (200 C). Line baking sheet with parchment paper.
In a large bowl, combine flours, brown sugar, baking powder, spices, xanthan gum, and salt.
Chop chilled butter into small cubes. Cut butter into flour mixture using a fork (or two!) or a pastry cutter until distributed throughout, and the mixture forms a coarse meal - it'll resemble gravel.
In a small bowl, whisk together ⅔ cup milk, molasses, the egg, and the vanilla extract.
Add the wet mixture to the bowl of dry ingredients, stir JUST until combined - mixture will be a little sticky.
Place dough onto a lightly floured work surface, sprinkling some flour on top. Gently knead for a few seconds, then gather dough up into a ball.
Press down to a disk that’s an even 1" thickness, cut into 6 wedges.
Transfer scones to the lined baking sheet, brush the top of the scones with a little bit of the remaining milk.
If you'd like, scatter coarse sugar over top of the unbaked scones.
Bake for about 25 minutes or until golden brown.