Whisk together flour, baking soda, salt, and cocoa powder. Once combined set aside.
Using a stand mixer or electric mixer beat softened butter with melted chocolate, sugar, and brown sugar. Once well combined add in the egg, vanilla extract, and milk. Add in dry ingredients and mix until well-combined.
Place dough in the fridge and allow to chill for at least 2 hours.
Preheat oven to 350 degrees F. Prepare a baking sheet with parchment paper
Place your Christmas sprinkles on a plate and roll each cookie dough ball around it until the cookie is covered. Place them on your baking sheet.
Bake for 12-13 minutes. Allow cooling on the pan for several minutes.
For this recipe chilling the cookies is a must. To make these cookies really soft and gooey I add melted chocolate right into the dough.This will make your cookies perfect but hard to handle without chilling. Once everything is mixed you can cover them and chill for at least 2 hours but you could chill them overnight also.If properly stored this dough will be good for 2-3 days in the fridge. If you are chilling for more than 2 hours you might want to let them sit on the counter for 15 minutes so they are easier to scoop.