Prep ice cream maker according to instructions - for me that means placing the mixing bowl into the freezer at least 15hrs in advance.
For the ice cream, combine heavy cream, half and half, sugar, and vanilla in a medium mixing bowl until fully mixed, there will probably be some undissolved sugar but that's fine.
Pour mixture into ice cream maker and prepare according to the manufacturer's instructions.
While the ice cream is mixing, take that time to chop the chocolate and the graham crackers and prep the marshmallow creme. I cut the chocolate into slivers so that it wouldn't become super hard in the freezer. The graham crackers I was more willy nilly about, just kind of broke them up into different sized pieces.
When the ice cream has a few minutes left to mix add in the graham crackers and the chocolate. This way they will be well dispersed but won't affect the freezing process.
Once the ice cream has finished mixing, you should have something that is soft-serve consistency, so you could totally eat it right away. If you do that I suggest some marshmallow on top and maybe even some hot fudge and extra graham cracker crumbs on top, but that's me.
If you want to let it harden a bit more, which I do recommend, transfer to an airtight container that will go into the freezer. It is here that you will add the marshmallow creme. I added it in layers to ensure a nice ribbon. I started with a layer of ice cream then added a layer of marshmallow on top, I continued this until everything was in the container.
Place the container of ice cream in the freezer for at least 3 hours - again, you can eat it at any time, but I like the texture once it has hardened a little - or up to a few days.
When you are ready to eat take the container out of the fridge for a few minutes to soften a tiny bit, then eat your heart out!