Warm buttermilk in the microwave (roughly 100ºF) and combine with oil and vanilla. Set aside
Whisk together the flour, baking soda, baking powder, sifted cocoa powder and espresso powder. Set aside.
Cream together the butter, white sugar, sifted brown sugar and salt with the whisk attachment until light and fluffy. Switch to the paddle attachment if you have one. *see notes*
Add in the eggs one at a time while mixing on low. Letting the first one mix in before adding the second.
Scrape the bowl to be sure that everything is mixed well.
While mixing on low, add in 1/3 of your flour mixture, followed by 1/3 of your buttermilk mixture. Alternate two more times until just combined.
Fill your cupcake liners 2/3 of the way full and bake for 18-20 minutes until set. Do not overbake.
Let cool completely before frosting