Preheat oven to 350°F (175°C). Line a muffin tin with cupcake liners.
In a large bowl, whisk together: flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Add: egg, milk, oil and vanilla
Mix until combined.
Slowly pour in the hot coffee or water and stir. Batter will look thin, that’s correct!
Fill liners about 2/3 full.
Bake 18–22 minutes or until a toothpick comes out with just a few moist crumbs.
Cool completely before frosting (this part matters more than people think, warm cupcakes melt buttercream fast).