Preheat the oven to 350F (180C) degrees and line a muffin tin with muffin papers. You'll end up with 6 or 7 cupcakes in total. I always use the middle 6 muffin cavities because I find the cupcakes cook more evenly.
In a medium bowl whisk together the flour, cocoa, baking soda, baking powder and salt.
In a separate medium bowl whisk together the oil, sugar, vanilla extract and egg. Then whisk in the buttermilk.
Whisk the dry ingredients into the wet ingredients until no lumps remain.
Spoon the batter into the prepared muffin tin, filling each about ½ - ⅔ full. You should end up with 6 or 7 cupcakes total. Be sure not to fill the cupcake liners to the top.
Bake in the preheated oven for 18-20 minutes, or until an inserted toothpick comes out clean.
In a medium bowl, beat the butter until soft.
Beat in 1 cup powdered sugar. If it's lumpy, be sure to sift it first.
Add in the cocoa powder (again, sifting if lumpy), vanilla extract and salt and beat until combined.
Mix in the rest of the powdered sugar about ½ cup at a time, alternating with a tablespoon of milk/cream until the desired sweetness and thickness is reached.
Frost the cooled cupcakes with a knife, or transfer the frosting to a piping bag and frost. I used a piping bag and a Wilton 1M piping tip.
