Preheat the oven to 180 degrees C. Grease and line a 23cm springform cake tin so that the baking paper comes up about 2 cm on the sides.
Place the chocolate chips, coffee and water in a microwave safe bowl. Microwave until chocolate is almost melted. Remove and whisk until mixture is smooth. Set aside to cool.
Using a hand held mixer, beat butter and margarine together in a large bowl until creamy. Gradually beat in sugar until light and fluffy.
Gradually beat in egg yolks one at a time, beating well after each addition. Slowly add the flour and beat at a low speed. Add the cooled chocolate to the mix and beat again.
In a separate bowl, beat the egg whites until stiff. Fold egg white mixture, one third at a time, into the chocolate mixture until blended thoroughly.
Pour the mixture into the cake tin. Bake for 1 hour. The cake is ready when a skewer inserted about 2cm from the side of the tin comes out clean. Note that the cake is very dense, so the top may crack when baking.
Cool in the tin for 10 minutes to allow the cake to set. Then remove from the tin, and allow to cool completely, which may take several hours.
This cake is definitely "rich, dense and moist" and good tip about leaving it to cool all the way. I let it cool in the cake tin. But I found it a bit too sweet for our tastes. Next time I would reduce the sugar a bit. - 01 Mar 2010