Melt the butter in a large pan or dutch oven.
Add in the marshmallows and melt over medium/low heat, stirring occasionally until fully melted.
Add in the vanilla, rice krispies and crushed graham crackers. Fold to combine. it helps to lightly grease your spatula so it's not too sticky.
Let cool for 5-10 minutes, then fold in the chopped chocolate just until combined.
Press into a greased 9x9 inch baking pan. I like to press on extra marshmallows, chocolate and graham crackers on top, but this is optional!
Set aside to set for 1 hour, then slice into 12-16 squares and enjoy!