Using your electric mixer, beat together the butter and both sugars for a couple of minutes until fluffy, then add the egg and vanilla and beat again until combined – scrape down the sides if needed.  In a separate small bowl, whisk together the flour, cocoa, baking soda and salt and with the mixer on low, slowly add the dry to the wet and mix on low until combined.  The dough will be thick, scrape down the sides and bottom, add the milk and beat on high for a quick minute to finish.  The dough should now be very sticky.

It will be impossible to work with at this point, but to make it easier on myself, I weighed and fashioned 25 gram blobs onto a small baking sheet, and when all of the dough was measured out I covered the pan with plastic wrap and chilled it for a couple of hours.  You could also simply chill the dough as is and then weigh and roll each cookie ball, but I think pre-measured blobs are more efficient.

However you get there, when you’re ready to get baking, preheat the oven to  350 and line a couple of large baking sheets with parchment.  Roll each chilled blob into a ball, generously roll each ball in the sugar and arrange on your prepared baking sheets – you should end up with about 2 dozen balls.

Bake for 10 to 12 minutes until the edges appear set and the tops are crackly-looking like gingersnaps.  Remove the cookies from the oven and allow to rest/cool for 2 minutes, press an Andes mint into the top of each hot cookie, let the chocolate sit for 5 minutes, then take the end of a sharp knife and swirl/spread the melted chocolate.

Transfer all to a rack and allow the cookies to cool completely before storing or freezing – everyone loved these!