Make the cupcakes

1. Preheat oven to 300°F (148°C) and prepare a cupcake pan with liners.
2. Add the flour, sugar, cocoa powder, baking soda and salt to a large mixing bowl and combine. Set aside.
3. Add the egg, milk, vegetable oil and vanilla extract to another medium sized bowl and whisk together to combine.
4. Add the wet ingredients to the dry ingredients and mix until well combined.
5. Add the water to the batter and mix until well combined. The batter will be very thin.
6. Fill the cupcake liners about half way and bake for 18-23 minutes, or until a toothpick comes out with a few moist crumbs.
7. Remove the cupcakes from oven and allow to cool for 2 minutes, then remove to a cooling rack to finish cooling.

Make the buttercream

1. When the cupcakes have cooled, make the buttercream. Add the butter to a large mixer bowl and beat the butter until smooth.
2. Add half of the powdered sugar and beat until smooth.
3. Add the vanilla extract and 2 tbsp of cream and mix until well combined and smooth.
4. Add the Oreo crumbs and mix until combined. Add the remaining powdered sugar and beat until well combined and smooth.
5. Add an additional 2-3 tablespoons of cream, as needed, until you have the right consistency.
6. To decorate the cupcakes, fit a piping bag with a large round piping tip (I use Ateco tip #809) and pipe frosting onto cupcakes. Finish the cupcakes off with an Oreo.