In a large pot melt and brown the butter. Constantly stir the butter until it melts and starts to turn brown and give off a nutty aroma. This will take 3-5 minutes. When it starts to brown, immediately remove from the heat. Stir in 2 teaspoons of vanilla extract.
Using a rubber spatula, stir in 20 ounces of marshmallows and stir until completely melted. once melted, stir in Rice Krispies, 2 cups at a time, until combined. Dice up Graham crackers into ½ inch pieces or smaller and stir into the mix.
At this point I let the mixture cool for about 5 minutes while I line a 9x13 inch baking dis with parchment paper. You can also spray with nonstick cooking spray. Melt 4 ounces of chocolate in the microwave, 30 seconds at a time and stirring in between, until completely melted. Set aside.
Stir in the rest of the mini marshmallows until just combined, you don't want these to melt as much! Finally stir in the chocolate chips and pour into the pan. Use parchment paper to press down into the pan, or spray your hands with nonstick cooking spray.
Lift the Rice Krispies out of the pan (if you are using parchment, if not, you can leave in the pan) and drizzle the melted chocolate over top. Cut into 12 even treats and serve!