Preheat oven to 350 degrees F.
In a large bowl combine graham cracker crumbs and sugar. Stir until well mixed.
Pour melted butter into bowl and stir together until the graham cracker crumbs are evenly moistened by the butter.
Firmly press the graham cracker crumbs into the bottom of a 9x13 inch baking pan to create an even layer. Make sure to pack the crust down tightly to ensure a firm crust.
Bake for 10 minutes until the edges are lightly brown. Remove from the oven and let cool completely.
In a microwave-safe bowl combine chocolate chips and sweetened condensed milk. Place in microwave and heat for 3 minutes. Remove from microwave and stir until the chocolate is melted and smooth. If needed you can continue to microwave for 1 minute at a time, stirring in between, until all of the chocolate is melted.
Add 2 cups of marshmallows to the chocolate and gently fold them in.
Pour the fudge over the graham cracker crust and spread out to make an even layer.
Top with roughly chopped Butterfinger Minis pressing them down firmly into the fudge.
Place in refrigerator and chill for 1 hour.
Cut and serve.