In a medium bowl, cream the butter and brown sugar together until the mixture becomes light and airy (with a KitchenAid, about 2 minutes. with a manual whisk, about 5 minutes). Add in the egg, vanilla and peppermint extract.
In another bowl, sift together the flour, cocoa powder, baking soda, and salt. Next, add the dry ingredients into the butter mixture, stirring until just combined. Gently fold in the white chocolate chips, being careful not to overmix the dough.
Scoop roughly 1½ inch spheres of dough onto a cookie sheet, leaving about 2 inches of space in between each ball of dough. Bake for 10-12 minutes, being sure to keep an eye on the consistency of the baking cookies. Allow to come to room temperature on a cooling rack.
To make the white chocolate, place chopped white chocolate and coconut oil over a double boiler and stir gently until melted. Dip each cookie into the white chocolate, sprinkle with crushed peppermint candies, then place back on cooling rack until the chocolate hardens.