Prepare a 9×13-inch pan by spraying it with butter cooking spray. Set aside.
In a large pot over medium heat, melt the butter and salt. Use a rubber spatula to spread the butter up the sides to prevent the mixture from sticking.
Add 12 ounces of mini marshmallows. Stir over medium heat until the mixture is completely melted. Then remove from the heat.
Stir in the vanilla extract until well combined.
Add the 6 cups of Rice Krispies cereal and stir with a rubber spatula. Then add ¾ of the broken graham cracker pieces, chocolate chips, and the remaining marshmallows. Stir to combine.
Pour the mixture into the prepared 9×13-inch pan. Add the remaining graham cracker pieces and Hershey pieces on top. Wet your hands, shake off the excess water, and use your hands to gently press the Rice Krispies into the pan. Don't press them down too hard, or they'll be hard to bite into! Let the treats cool at room temperature for an hour.
Using the rubber spatula, remove the treats from the pan. Use a knife to cut them into squares and enjoy!