One of Nigella's cakes. I have adapted it a bit for muffins. It can make about 24 regular sized muffins and 48 mini muffins. It seems complicated but its worth it!
Preheat oven to 180C and line 12 cup muffin tin with papers.
In a large bowl sift together the flour, sugars, cocoa, baking powder, bicarbonate and salt.
In another bowl whisk together the eggs, sour cream and vanilla until blended.
In a third bowl, using a hand mixer, beat together the melted butter and oil until just blended then beat in the water (yes this really works).
Add the dry ingredients to the oil mixture all at once and mix on low speed.
Add the egg mixture and beat until everything is blended well.
Fill each muffin cup 3/4 full and bake in the oven for 20-25 minutes or until a skewer comes out clean.
Cool on wire rack while making icing.
--To make the icing--
Melt the chocolate in the microwave (2-3 mins on medium) and let in cool slightly.
In a large bowl beat the butter until it is soft and creamy and then add the sifted icing sugar and beat again until everything is light and fluffy.
Gently add the vanilla and chocolate and beat until smooth.
Ice the cupcakes with a spatula or piping bag.