Place Shirley J Mugging Chocolate Brownie Mix in a (2-cup) microwave safe mug. Add warm water & mix vigorously with a fork until well-blended.
Microwave 90-seconds (based on an 1100 watt oven) or until done. May check doneness by inserting a toothpick into the center; if it comes out clean, it's done.
Immediately top with chocolate chips. Allow to melt & spread over the top of the cake.
Toast marshmallows with a fork over a small candle (toasting the marshmallows is optional.) Place marshmallows onto the top of the cooked mug cake, & return to microwave for an additional 20 seconds or until marshmallows puff up. Remove & top with crumbled graham cracker & additional chocolate chips, if desired. Enjoy warm & gooey!