Line a 8" x 8" baking pan with parchment and grease the parchment.
Preheat oven to 350 degrees.
Stir together graham cracker crumbs, chocolate chips, and sweetened condensed milk until well combined.
Spread into prepared pan.
Bake approximately 30 minutes or until set and golden.
Put marshmallows on top of bars and place back in the oven. Turn on the broiler and broil until marshmallows are toasted. Be sure to watch this carefully as you don't want to burn the marshmallows or catch the parchment on fire.
Cool completely in pan before cutting.
Recipe by From Calculu∫ to Cupcake∫ at https://www.fromcalculustocupcakes.com/smore-bars/