Preheat oven to 350° F. Line 24 cupcake tins with paper liners (or, more realistically, 12 at a time).
In a large bowl, stir together the flour, brown sugar, cocoa, baking powder, baking soda and salt. Break up any lumps of brown sugar and cocoa.
Add the milk, oil, eggs and vanilla and beat with an electric mixer on medium speed for about 2 minutes. Add the coffee and beat on low speed just until blended. The batter will be thin.
Divide the batter among the tins, filling them about 2/3 full, and bake for 25 minutes, until the tops are springy to the touch. Tip them a bit in their pans to let the steam escape and help them cool. Wait until they are completely cool before frosting them. These are delicious absolutely plain.