1In a medium saucepan, heat the whole milk over medium heat until it begins to steam, but do not let it boil.
Whisk in the unsweetened cocoa powder and granulated sugar until fully dissolved.
Add the dark chocolate chips and stir until they are completely melted and the mixture is smooth.
Stir in the vanilla extract and Nutella, and continue to whisk until the Nutella is fully incorporated and the hot chocolate is smooth and creamy.
Remove from heat and pour the hot chocolate into mugs.
Serve immediately, optionally topped with whipped cream or marshmallows.