In a medium saucepan, heat milk over medium heat until it comes to a simmer. Add chocolate and cocoa powder and whisk until melted. Add sweetener to taste.

Rub a melted marshmallow along the rim of each mug. Pour graham cracker crumbs onto a plate and dip the mugs into the crumbs until the rims are well coated.

Pour hot chocolate into the mugs and add marshmallows on top. Using a kitchen torch, toast marshmallows until brown.

Drizzle chocolate syrup on top and serve immediately.