Mix graham cracker crumbs and melted butter into bottom of mug and press down with a spoon to pack it to the bottom of the mug.

In a separate small bowl, place chocolate and 3 tbsp of milk. Microwave for 30 seconds and stir until chocolate is melted. If chocolate is not completely melted, heat for another 15 seconds and stir again. Careful not to microwave more than 30 seconds at a time as the milk will bubble over. Add in flour, baking powder and whisk. Batter will be quite thick. Whisk in remaining 1 tbsp milk until batter is smooth. Pour into mug on top of the graham cracker crust.

Cook in microwave for 1 minute. Top of cake should be dry and cake should look done. Top with mini marshmallows. If you have a kitchen torch, torch the marshmallows before eating. You can also roasted marshmallows in oven. Turn oven to 375°F and heat mug for about 5 minutes until marshmallow tops begin to turn light brown.