Chocolate Potato Cake

The original recipe of this came from The Global Gourmet.  The potatoes are used as the liquid component of the cake instead of milk, so it could be made dairy free if margarine was used instead of butter.  I make this recipe with fresh potatoes as the instant mashed potatoes contain preservatives.  The cake is very moist and keeps well.  I took some to work and there were a few pieces left after 4 days, and it was still moist.  It is also great as a dessert, warm with custard or ice cream.