Add marshmallows and milk to a saucepan over low heat. Stir constantly until the marshmallows are melted. Let cool while you prepare the rest of the recipe.
Beat whipping cream with an electric mixer until soft peaks form. Fold into marshmallow mixture.
In a bowl, mix together graham cracker crumbs, chocolate and butter. Press 1/2 of mixture into the bottom of a 9-inch pie pan.
Spread marshmallow mixture into pie pan. Top with remaining graham cracker crumbs mixture.