1. Preheat the oven to 350°F (176°C) and prepare a cupcake pan with cupcake liners.
2. To make the cupcakes, combine the flour, cocoa, baking soda and salt in a medium sized bowl and set aside.
3. Add the butter, sugar, oil and vanilla extract to and large mixer bowl and beat together until light in color and fluffy, about 3-4 minutes. Do not skimp on the creaming time.
4. Add the eggs one at a time, mixing until mostly combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
5. Add half of the dry ingredients to the batter and mix until mostly combined.
6. Slowly add the milk and mix until well combined. The batter will look curdled, but that’s ok.
7. Add the remaining dry ingredients and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Do not over mix the batter.
8. Fill the cupcake liners about three quarters full. Bake for 16-18 minutes, or until a toothpick inserted comes out with a few crumbs.
8. Remove cupcakes from oven and allow to cool for 2-3 minutes, then remove to cooling rack to finish cooling.
9. Once cool, use a cupcake corer to remove the centers of the cupcakes.
10. Fill the centers with marshmallow fluff, about 1 1/2 to 2 tablespoons per cupcake.
8. To make the frosting, beat the butter in a large mixer bowl and mix until smooth.
9. Add the melted chocolate and mix until well combined.
10. Add the cocoa powder and mix until well combined.
11. Add about half of powdered sugar and 2 tablespoons of heavy cream and mix until well combined.
12. Add remaining powdered sugar and salt and mix until smooth.
13. Add remaining heavy cream as needed to get the right consistency of frosting.
14. Pipe the frosting onto the cupcakes (I used Ateco tip 844). Add a few marshmallow bits per cupcake.
15. To make the chocolate ganache, add the chocolate chips to a small bowl. Heat the heavy whipping cream in the microwave just until it begins to boil, then pour over the chocolate chips. Allow to sit for 2-3 minutes, then whisk until smooth.
16. Drizzle some chocolate ganache over each cupcake, then sprinkle on some cookie crumbles.

* I used most of a 7oz jar of marshmallow fluff.