Preheat the oven to 350°F and line two standard muffin cups with liners.
In a medium bowl, mix together the oil, egg white, vanilla, and milk with a fork to combine.
Mix in the sugar followed by the flour, cocoa powder, baking powder, and salt.
Divide the batter among the muffin cups.
Bake for 18-20 minutes until they are set on top, a toothpick comes out with just moist crumbs, and if you gently press the top of the cupcake it slightly bounces back.
While the cupcakes cool, make the frosting. Stir together the butter and milk with a fork in a small bowl - it doesn’t need to be completely combined.
Mix in the powdered sugar, cocoa powder, and vanilla. You can add more or less powdered sugar/milk to adjust the consistency.
Either pipe on the frosting or spoon it on top of the cooled cupcakes and enjoy!
