Add 3 cups of milk and 2 cups of half-and-half into the slow cooker.
To a blender, add the remaining 3 cups of milk, the Andes mints, cocoa powder, and sugar. Blend on high until the mints are chopped up and the cocoa powder is mixed in, about 15-20 seconds. Pour the mint mixture into the slow cooker and stir to combine.
Place the lid onto your slow cooker and cook for 3-4 hours on HIGH. Make sure to stir every hour to help prevent the cocoa from scalding on the bottom of the crock.
Serve warm in mugs topped with your favorite toppings if desired.
Notes
You'll need about 1 1/2 box of Andes mints for the hot chcoolate.