Preheat the oven to 350ºF and line a cookie sheet with parchment paper or a silpat mat. Set aside.
In a medium bowl whisk together the coconut flour, cocoa powder, espresso powder (if using), baking soda and salt and set aside.
Beat the coconut oil and coconut sugar together. It will be pretty crumbly at first then start to come together and smooth. Add the eggs, peppermint extract and vanilla and mix until smooth, 1-2 minutes.
Slowly add the dry ingredients to the wet ingredients and beat on low until incorporated. Stir in dark chocolate with a rubber spatula.
Use a large tablespoon or cookie scoop and place cookie dough 2 inches apart on the prepared baking sheet. Top each cookie with extra chocolate chunks if desired before baking. Bake for 8-10 minutes or until they’re set around the edges and top. When they come out of the oven lift the edges of the cookie sheet (using hot pads) and bang the baking pan against the stove or counter a few times to flatten the cookies.
Allow to cool for 3-5 minutes on the cookie sheet, then transfer to wire rack to cool completely.
For the topping, melt the chocolate in the microwave in 30 second intervals. Place a piece of parchment paper under the cooling rack to catch any extra chocolate. Use a spoon to drizzle the melted chocolate back and forth across the cookies. Top with crushed peppermint candies.