In a mixing bowl, add in the butter and granulated sugar. Mix on medium until light and fluffy. Scrape down the sides.
Add in the egg and vanilla and mix until incorporated.
Sift the cocoa powder and flour into the mixing bowl to avoid lumps of cocoa powder in the cookie dough. Mix on low until the flour is just incorporated.
Press bits of the chocolate dough into a non-stick mini cheesecake pan with the removable bottoms. (A picture and link to one is under the recipe) Using the dull side of a butter knife, I scrape the dough off even with the top of the pan.
Place in a 350 degree oven for 14 minutes. The centers of the cookie will be puffed up. Let the cookies cool for about 5 - 10 minutes in the pan. Using a small fondant rolling pin (spoon could work) press down the centers of the cookies. This will make room for the mints and marshmallow goo. Remove from pan and set aside to cool completely.
Once the cookies are completely cool, place the melting chocolates into a microwave safe bowl and microwave for 30 seconds. Stir. If not completely smooth, microwave for another 20-30 seconds and stir again.
Dip the rims of the cookies into the melting chocolate and set aside to dry. It should only take 10..ish minutes.
Filling
Fill the cups about ¾ full with the chopped Andes mints/thins.
Spray a microwavable bowl with non-stick cooking spray. Place the marshmallows in the bowl and microwave for 30 seconds. Stir with a spatula that has also been sprayed with non-stick cooking spray. If it's not completely smooth, microwave for another 15 seconds.
Stir in the peppermint extract and gel paste color.
While the marshmallows are still warm, place into a disposable piping bag or a sandwich bag. Cut a small hole in the tip and pipe the marshmallow on top of the Andes mints/thins.
Break a pretzel stick in half and place a half in each cookie cauldron.