In a small slow cooker, whisk together all ingredients.
Cover, and heat on low for 2 hours, whisking regularly.
Pour into mugs, top with marshmallows and/or whipped cream.
To make this crockpot hot chocolate faster:Blend all the ingredients in a microwave-safe bowl. Cook in the microwave, whisking often, in 1-minute increments until chocolate is melted, and drink is smooth. Serve immediately, or keep warm in a small slow cooker.To make this recipe aheadMake as written, and refrigerate. Whisk well before adding to the slow cooker.