Preheat the oven to 300F and line two baking sheets with parchment paper.
In a large bowl, combine almond flour, cocao powder, sweetener, baking powder and salt. Add in egg, butter, vanilla and stevia and stir well until dough comes together.
Roll out dough between two pieces of parchment paper to desired thickness (I rolled mine very thin, about 1/8 inch thick). Lift off top piece of parchment and set aside. Using a 2-inch diameter cookie cutter, cut out circles of dough and lift gently. Place cookies on prepared baking sheet. Gather up scraps of dough and reroll until too little is left to roll out.
Bake cookies until firm to the touch, about 30 minutes. Remove and let cool (they will continue to crisp up as they cool).
Place a metal bowl over a pot of gently simmering water, not allowing the bowl to touch the water. Melt butter and chocolate together in the bowl, stirring until smooth. Remove from heat and stir in peppermint extract.
Dip cookies into chocolate, using two forks to turn over and fully coat cookie. Gently pass chocolate-coated cookie back and forth between forks to remove excess chocolate, then place on waxed paper to cool and set.