Add the heavy cream, milk, chocolate chips, condensed milk, and vanilla to a slow cooker. Stir gently to combine.
Cover and cook on low for 2-3 hours, stirring about every 20 minutes, until the chocolate is melted and fully combined.
Add green and yellow food coloring until you reach your desired shade of green. Serve with your desired toppings, such as whipped cream, marshmallows, sprinkles, or crushed candy canes!
You can keep the hot chocolate on the warm setting for up to 3 hours for serving. If the hot chocolate gets too thick while it sits, you can stir in more milk to your desired thickness.
Notes
Use a high-quality white chocolate for best results. You can use chips, chopped white chocolate bars, or melting discs.
Be sure to give the hot chocolate a stir every 20 minutes or so, so that the chocolate will not burn on the sides and it heats evenly.