Position the oven rack in the centre of the oven. Preheat the oven to 180 degrees C. Line a 25cm round cake tin with a circle of baking paper.
Peel, slice and cut the ginger until very fine (or use a grater). Mix together the molasses, sugar and oil. In another bowl, sift together the flour, cinnamon, cloves and black pepper.
Bring the water to the boil in a saucepan, stir in the baking soda and mix the hot water into the molasses mixture. Stir in the ginger.
Gradually whisk the dry ingredients into the mixture. Add the eggs and continue mixing until everything is thoroughly combined. Pour the batter into the prepared cake tin and bake for about 1 hour until the top of the cake springs back lightly when pressed or a toothpick inserted into the centre comes out clean. If the top of the cake browns too quickly before the cake is done, drape a piece of foil over it and continue baking.