Start by lining a cookie sheet with parchment paper – set aside.
In a large bowl, combine the sugar cookie mix with the butter and milk. You may find it is easiest to mix this dough with your hands.
In a medium microwave-safe bowl, melt half the candy melts per the instructions on the bag. Once smooth, pour the candy melts onto the parchment paper and spread to about ¼ inch thick. Working with a little dough at a time, top the chocolate with the dough. Refrigerate for 10-15 minutes until it is starting to harden.
Melt the remaining candy melts and pour over the top of the dough spreading it with a spatula. Top with sprinkles or other decorations.
Chill for 1 hour until completely hardened, then break apart and package up.