In a slow cooker, combine the milk, heavy cream, nutella, cocoa powder, vanilla extract, and granulated sugar. Stir well to ensure the nutella is fully incorporated.
Cover the slow cooker and cook on low heat for 2 hours, stirring occasionally to prevent any scorching.
Ladle the Nutella hot chocolate into mugs. Top each mug with marshmallow and chocolate syrup if desired.
Serve the hot chocolate immediately and enjoy!
Notes
● Adjust the sweetness of the hot chocolate by adding more or less sugar, depending on your preference.
● Feel free to add a touch of cinnamon or a dash of nutmeg for extra flavor.
● If desired, you can spike the hot chocolate with a shot of your favorite liqueur, such as Bailey's Irish Cream or hazelnut liqueur.
● Leftover hot chocolate can be stored in the refrigerator for up to 3 days. Reheat gently on the stovetop or in the microwave before serving.