Chocolate S'mores Cake in the Crockpot

1 box chocolate cake mix (I used a Devil's Food mix), mixed as box explains
1 cup chocolate chips (optional)
1 cup marshmallows, any size, cut into small pieces if large
4 whole Graham Crackers, crumbles into small pieces

Line your slow cooker with foil so that it extends 2 inches up from the side all along the edges and grease well. Turn the slow cooker to high.
Mix the cake batter, adding the chocolate chips at the end, if using. Pour the batter into the foil. Cover and cook on HIGH for 4 hours, making sure a toothpick inserted in the middle comes out clean. Turn off the slow cooker and remove the lid. Let the cake sit for 10 minutes.
Sprinkle the marshmallows on top. Preheat your oven broiler. Pull the cake out of the slow cooker (just gently lift the foil up) and place the cake under the broiler for 40-60 SECONDS. The marshmallows brown quickly so keep a close eye on them! Remove from the broiler and sprinkle with Graham Cracker bits. Let the cake cool for 5-10 minutes before serving