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. To make the frosting, combine the butter and shortening in a large mixer bowl and mix until smooth.
10. Add 2 cups of powdered sugar and mix until smooth.
11. Add the vanilla and mint extracts and 1 tablespoon of water or milk and mix until smooth.
12. Add remaining powdered sugar and mix until smooth.
13. Add remaining water or milk as needed and mix until smooth.
14. Pipe the frosting onto the cupcakes. I used a large round tip to pipe frosting evenly on to the top, then smoothed the top and sides with an offset spatula.
15. Add mini chocolate chips to a small bowl (or hold some in your hand) and dip the sides of the frosting into the chips so that they stick.