Preheat oven to 350°F. Spray donut pan with non-stick spray and set aside.
Pulse the graham crackers (about 4) in a food processor until you have a little more than ¼ cup of crumbs.
In a small bowl, whisk together the flour, unsweetened cocoa powder, 2 tablespoons of graham cracker crumbs, baking powder, and salt.
In a separate bowl, whisk together the vegetable oil, sugar, and brown sugar until smooth. Add in the eggs and vanilla and whisk until fully incorporated.
Mix half of the dry ingredients into the egg mixture, then add in the milk. Once incorporated, add in the remaining dry ingredients and mix until just combined.
Transfer the batter to a piping bag, then cut of the tip and pipe into the donut pan, filling about halfway. You can also just spoon the batter into the pan if desired.
Bake at 350°F for 8-10 minutes or until a cake tester comes out clean. Invert the donut pan on a cooling rack, and the donuts should slide right out!
While the donuts are cooling, make the chocolate glaze!
Add the chopped dark chocolate, butter, and cream to a microwave safe bowl. Microwave for 30 seconds, then stir. Repeat until the chocolate is fully melted and the glaze is thick and glossy.
Dip the donuts into the glaze and place back on the cooling rack so any excess can drip off.
While the glaze is still wet, gently press mini marshmallows on top of the donuts so that they stick to the glaze. Then sprinkle with leftover graham cracker crumbs.