Preheat oven to 350 degrees F and line a muffin tin with 7 liners
In a medium bowl, whisk together flour, cocoa powder, baking powder, baking soda and salt.
In a separate bowl, whisk together egg, sugars, oil and vanilla.
Add half of wet ingredients and half of butter milk to the dry ingredients. Whisk to combine.
Add the rest of the wet ingredients and buttermilk to the dry ingredients and mix until it just combined. Do not overmix.
Fill cupcake liners with batter halfway.
Bake for 18 minutes or until a toothpick in the center comes out clean.
Let cool and then frost with desired buttercream!