Preheat your oven to 375 degrees F. Line the bottom of an 8-inch square pan with aluminum foil or parchment paper.
Combine the crushed graham crackers, sugar, and melted butter in a medium bowl. Smash with a fork until everything is moist and then pour into the pan.
Using your fingers, press the crumbs down firmly until the graham crackers cover the bottom of the pan evenly.
Bake for approximately 7 minutes, then remove from the oven and set aside.
Add chocolate chips to a microwave safe bowl.
Microwave on high for 1 minute. Stir and then microwave for 15-second intervals, stirring after each one, until melted and smooth.
Pour the melted chocolate over the graham cracker crust and spread to evenly cover the crust.
Add the marshmallows and butter to a large microwave safe bowl.
Microwave for 1 minute, stir, and then microwave for another 1-2 minutes until melted and smooth.
Stir in the Rice Krispies, then pour into the pan on top of the chocolate.
Using wet fingers, press the Rice Krispies down firmly and top with extra chocolate chips, if desired.
Let fully cool before lifting out the pan and cutting into bars.