This is the recipe we used for Paula's 40th Birthday Cupcakes and it is/can be totally vegan! It's in American measurements but we've converted some of them to weights (which are very approximate). 

Vegan Chocolate Cake

1.5 cups flour

3 Tb cocoa powder

1tsp bicarbonite of soda

1 cup sugar

1/2 tsp salt

Sift all of the above in a big bowl and mix well - a wooden or metal spoon will do you fine.

Then make 3 grooves in the dry mixture.  Into one groove each pour:

5 Tb veg oil

1 Tb vinegar

1 tsp vanilla

Then pour 1 cup water over the whole thing and mix until you can't see the flour anymore and there aren't any big lumps.

Divide into a muffin pan (either a greased and floured tin or a tin preloaded with cup cake cases).  This batch makes 12-14 cupcakes but you can easily double it up and it is still easy to mix, pour etc as long as you have 2 muffin tins to hand.

Bake at 350 F for 22 minutes or until a knife comes out clean.

You can add anything you like to the recipe.  We added frozen rasberries (these won the taste test hands down over the tinned ones) but you could also add chocolate chips or nuts. The frozen raspberries taste best if they go in straight from the Freezer. We've no idea why but they make the batter much less gluey than defrosted raspberries and totally hold their shape and bite this way.

Once baked let the cake cool in the tins for a short while then transfer to wire racks. When totally cooled they are ready to frost.

Frosting

Around 1/3 tub of Pure (or another tasty dairy free margerine)

Around 1 lb icing sugar (or powdered sugar if you are an american)

Gel or powdered food dye (they give bright colours but don't give a nasty taste unlike the liquid ones)

Whip the Pure with a handmixer (or give it a hardcore go with a balloon whisk) and gradually add in the sugar until a fluffy but firmish frosting is achieved. Add colour and mix again til blended. Your icing is now ready for spreading over cakes or, much more authentically, piping on with a large mashed potato style nozzle.

OK, for conversions:

1 cup sugar weighs about 240 grams and is the same volume as 235 ml water

1.5 cups of flour weighs about 240 grams and is the same volume as 360 ml water

And, of course, 1 cup of water is equal to 235 ml.

Heather was recently asked about the texture in American muffins and cupcakes and how to get that chewy inside with a crispy outside. She thinks vegetable oil helps get that chewy texture but its really hard to get the crisp top using just veg oil. Heather reckons that this is the only very slight flaw in the vegan cup cake recipe and thinks the answer is buttermilk, yogurt, or sour cream.  All will give a really nice chewy and moist texture and still allow the butter to give it a crisp top.  The tangyness of yogurt and buttermilk tastes great in fruit muffins, especially, and sour cream works great with chocolate.