In a food processor (see notes above if you don't have one), combine the almond flour, cocoa powder, low carb sweetener, baking powder, and xanthan gum together by pulsing until mixed.
Add in the diced cold butter and the vanilla. Pulse again until the mixture is not longer dry but resembles bread crumbs. Then add in the egg and pulse again until the mixture looks like a thick cookie dough.
Dump the dough out on a long piece of parchment paper. I use the rubber spatula to create a more rectangular shape to the dough. Roll the dough up into the parchment paper to for a log. Create a log that is 10" long and twist off the sides tightly so that the dough will take the shape of the parchment paper. Place in the freezer for 45-50 minutes. If you plan on baking later (within 24 hours) refrigerate until ready to bake, then follow the freezer directions prior to baking.
Place in the freezer for 45-50 minutes or until solid to the touch, If you plan on baking at a later time, keep in the fridge and then place in the freezer prior to the actual bake time.
Once solid, remove from the freezer and with a sharp knife, slice 1/4" cookie dough rounds off of the log. You should get 30-32 cookies.
Preheat the oven to 350 F. Place parchment paper onto the cookie sheet. Bake for 11-13 minutes (my cookies liked the 13 minute mark). They will just get slightly brown right at the edge and will still be soft when you remove them from the oven. You need to let them set and fully cool for them to become crispier like a classic shortbread.
Once the cookies are fully cooled, melt the chocolate on half power in the microwave for 30 seconds and stir well. Continue this until it is fully melted. Stir in the mint extract to taste ( a little goes a long way).
Use a butter knife to spread a thin layer of chocolate onto the bottom of the cookies. Freeze until set and repeat for the top. Freeze again until set and then enjoy!
These can be stored up to a week on the counter or several weeks in the fridge or freezer (also this is obviously the way to go for eating them).