In your microwave-safe mug, add the 1/4 cup all-purpose flour, 1/4 cup brown sugar, 2 tablespoons cocoa powder, and a pinch of salt. Stir well to combine all the dry ingredients.
Next, pour in 2 tablespoons of milk, 2 tablespoons of vegetable oil, a splash of vanilla, and if you wish, a splash of coffee extract. Mix until the batter is smooth and fully combined.
Place your mug in the microwave and cook on high for about 1 minute and 30 seconds. Keep an eye on it while it cooks, as microwaves can vary in power. You want the brownie to look set but still moist in the center.
Once done, carefully remove the mug from the microwave (it will be hot!). Allow it to cool for a minute, then top with sweetened whipped cream if desired. Dig in with a spoon and savor the fudgy goodness!
