Preheat oven to 350°F. Line an 8×8 baking dish with parchment paper or foil. If foil, then also grease the bottom and sides. Set aside.
Process graham crackers using a food processor until fine crumbs. Add in melted butter and mix until the crumbs are completely coated in the butter.
6 tbsp butter, 2 cups graham cracker crumbs
Transfer into the prepared pan and press down firmly to create a base.
Begin sprinkling each ingredient onto the base; chocolate chips, peanut butter chips, graham crackers, and mini marshmallows.
3/4 cups chocolate chips, 1 1/2 cups mini marshmallows, 3/4 cups peanut butter chips, 5 graham crackers
Finish by pouring the entire can of sweetened condensed milk on top, covering the entire pan evenly.
1 can sweetened condensed milk
Bake for 25-28 minutes or until slightly golden brown. Remove from the oven and allow it to cool completely before slicing. As it cools, the bars will set.
Store in an airtight container at room temperature or in the refrigerator for up to 5 days. Enjoy!