Adding a small addition of liquor is a fun way to level up your hot chocolate. I would stick with 1 to 1 1/2 ounces of liquor but it is up to you. Basically, any liquor will work but here are a few recommendations: Baileys Irish Cream, Kahlúa, Spiced Rum, and even Red Wine. (Please drink responsibly and do not serve spiked hot chocolate to minors)