Preheat the oven to 350°F and line the baking sheet with parchment paper.
Combine the coconut sugar, flour, cocoa powder, and salt. Set aside.
In another bowl, combine the coconut oil, maple syrup, peppermint extract, non-dairy milk, and vanilla extract.
Add the wet mixture to the dry ingredients. Mix until well combined.
Dust a surface with flour and roll out the dough to about 1/16th inch thick.
Cut out the cookies with a small cookie cutter.
Transfer the cookies to the prepared baking sheet and bake for 8 to 10 minutes.
While waiting for the cookies to cool completely, melt the vegan dark chocolate chips, coconut oil, and peppermint extract in a double boiler over medium heat.
Melt until completely smooth, about 4 to 6 minutes. Stir continuously to keep the chocolate from burning.
Dip each cooled cookie into the chocolate coating, scraping the excess chocolate off the bottom of the cookies as needed.
Place the vegan thin mints on a wire rack with parchment paper underneath to allow the excess chocolate coating to drip.
Transfer the coated cookies to the freezer to set for 20 minutes.