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 ½ 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.

In a large bowl using a stand or hand-held electric mixer, beat the butter until fluffy.

Add in 2 cups powdered sugar, vanilla extract and salt and beat until combined starting with the mixer on a low speed.

Turn the mixer down to low speed and beat in the cocoa powder. If lumpy, be sure to sift the cocoa first.

Beat in the rest of the powdered sugar about ½ cup at a time, alternating with 1 tablespoon cream until the desired sweetness and thickness is reached.

Frost the cupcakes using a piping bag and your favorite cupcake piping tip (I used a 1M) or a flat edge knife. Optionally decorate with chocolate chips or sprinkles.