01 -
Place the graham crackers in a plastic bag and use a rolling pin to crush them into fine crumbs.
02 -
In a large bowl, whisk together the flour, 2 tablespoons graham cracker crumbs, sugar, baking powder and salt. Add the milk and egg and whisk until fully combined. Transfer the mixture to a microwave-safe mug.
03 -
Microwave the mixture on medium power for 2 minutes. Arrange the chopped chocolate on the surface of the cake and microwave again until the chocolate is melted, about 1 minute.
04 -
Top with marshmallow fluff or jumbo marshmallows. If desired, place under the broiler until marshmallow browns. Sprinkle with the remaining graham cracker crumbs before serving.