Whisk melted butter and egg together. Stir in the milk, vanilla and Sugar. Add flour and salt. Beat the batter until smooth.
Mix in graham crackers pieces, chocolate chips, and marshmallows. Pour into your mug(s)
Microwave for 1-1/2 to 2-1/2 minutes until it is firm. Allow to cool.
Notes
If you don't have self rising flour just whisk together 1 Cup of All Purpose Flour, 3/4 tsp. baking powder and a little salt... thats all now you are ready!