Preheat the oven to 180°C. Line 2 x 12 muffin tins with cupcake papers.
Stir the cocoa powder, coffee and brown sugar in a bowl and pour over the boiling water. Whisk to mix and set aside.
Cream the butter and caster sugar together until pale and fluffy and then add the vanilla extract.
Add the eggs one at a time, beating well after each addition.
Slowly add the flour, bicarb and baking powder. Pour in the cocoa/coffee mixture and beat until just combined.
Spoon the mixture into prepared muffin tins and fill approximately ¾ full (this recipe should make around 18 cupcakes)
Bake in the oven for 18-20 minutes or until the cupcakes slightly spring back when touched.
Allow the cupcakes to cool slightly in their tin before turning out onto a wire rack.