Preheat the oven to 350F (180C) degrees and a 12-cavity muffin pan with muffin papers.
In a large bowl whisk together the flour, cocoa, baking powder, baking soda, salt and sugar
In a separate large bowl whisk together the oil, egg, vanilla extract and milk. When finished, you should no longer see any pieces of egg.
Make a well in the middle of the dry ingredients and pour the wet ingredients into the well. Whisk together.
Once the batter is about 60-70% mixed, carefully pour in the hot coffee/boiling water and whisk everything together until smooth.
Spoon the batter into the prepared cupcake pan, filling each about 1/2 full. You should end up with 11 or 12 cupcakes. If you only get 9 or 10, the cupcakes are too full.
Bake 1 tray at a time on the middle rack of the preheated oven for 16-20 minutes, or until the tops feel slightly firm to the touch and an inserted toothpick comes out clean.
Let cool in the pan for 10-20 minutes, then transfer to a wire rack to continue cooling