Pour the rice krispies and oreos in a large mixing bowl. Set aside.
Melt the butter in a saucepan over medium high heat until melted. Turn the heat down to the lowest setting and add the marshmallows. Stir until the marshmallows are mostly all melted (this will take a few minutes--low and slow is key for perfect texture). Add in the vanilla and black food coloring (keep adding until you get the color you want) and finish melting.
Once fully melted, take them off heat and pour over the rice krispies. Stir to combine until everything is black. Dump everything by spoonfuls onto a greased cookie sheet, so they look like funky coal shapes. Allow them to cool about 20 minutes. Enjoy!