For the cupcakes:
Preheat oven to 350 degrees F.
Line 28-30 muffin tins with cupcake liners and set aside
Add about a tablespoon crushed graham crackers to the bottom of each cupcake liner
Sift together the flour, cocoa powder, baking powder, baking soda and salt in a medium size bowl
Add sugar and stir to mix
Pour flour mixture into a large mixing bowl and add eggs, oil, milk and vanilla
Beat on medium speed for 2 minutes, then stir in boiling hot water (consistency will be thin)
Fill cupcake liners 2/3 full with batter, pouring over graham crackers
Bake for 22-25 minutes and cool while you make your frosting
For the frosting:
Blend butter and cocoa powder in a mixer on low until smooth.
Slowly add powdered sugar, milk and vanilla until all sugar is incorporated. Add a little more milk, if needed, until desired spreading texture is achieved.
Frost cooled cupcakes and top with several mini marshmallows.
Use a kitchen blow torch, if you have one, to "roast" marshmallows