Can you make one of Nigella's Guinness Cake in slab form? If so how much cake should you make? Regards Kate
Nigella's Chocolate Guinness Cake (from Feast and on the Nigella website) makes a 23cm/9-inch round cake that is fairly deep. Usually if you want to convert from a round to a square pan then for this size of round cake you would need to use a 20cm/8-inch square cake pan, but it will need to be around 5cm/2 inches deep. Baking times are usually similar but you may want to rotate the square pan about 3/4 of the way through the cooking time to make sure the corners don't cook too quickly.
It is more difficult to convert the recipe for a rectangular pan but we would instead suggest looking at Nigella's Guinness Gingerbread recipe from Kitchen (p305). This is slightly similar to the Chocolate Guinness Cake though is slightly softer in texture. You could probably convert this to a chocolate version by omitting the spices (you may like to leave some cinnamon in) reducing the flour to 250g/1 2/3 cups and adding 50g/1/2 cup (unsweetened) cocoa powder. However we haven't tried this variation so cannot guarantee results.