Preheat oven or grill to 350°F.
Place a medium heat-proof bowl over a medium saucepan simmering with water. Add butter, ¼ cup of chocolate chips, and unsweetened chocolate and melt. Remove from heat and allow the mixture to cool down for 15 minutes.
In a small bowl, whisk together flour, baking powder, and salt.
In a large bowl, mix together the eggs, sugar, and vanilla. Add chocolate mixture and mix until well combined. Stir in the flour mixture. Add to the batter ¼ cup of chocolate chips, ½ cup of mini marshmallows, and 3 graham crackers roughly crumbled.
Pour mixture into an 8-inch skillet. Top with remaining mini marshmallows, chocolate chips, and graham crackers. Grill or bake for 10-12 minutes. Remove from grill. Allow 10 minutes for cooling and serve.