Combine the chocolate chips, nut butter, coconut milk, and coconut oil in a large glass or metal bowl. There's no need to mix at this point.

Fill a medium pot 2/3rds of the way with water and bring to a low simmer. Set the bowl over the pot of water (making a double boiler) and carefully stir the chocolate mixture to melt until totally creamy. Carefully remove the bowl and set it aside to cool for about 5 minutes.

While the fudge mixture cools, line a 9x5 loaf pan with parchment paper and lightly grease.

Carefully stir most of the crushed graham crackers and marshmallows into the fudge mixture. Press the fudge mixture into the loaf pan and flatten. Top the fudge with a few extra marshmallows and crushed graham cracker.

Transfer to the fridge and allow to set for 3-4 hours, until totally hardened. Slice and serve chilled.