For the Cake
1. Preheat the oven to gas mark 3/170° C and tear off a big piece of baking parchment to line the bottom and sides of a roasting tin of approximately 30 x 20 x 5cm deep.
2. In a decent-sized saucepan, melt the butter along with the sugars, golden syrup, treacle or molasses, cloves, cinnamon and ground ginger.
3. In a cup dissolve the bicarbonate of soda in the water.
4. Take the saucepan off the heat and beat in the eggs, milk and bicarb in its water.
5. Stir in the flour and cocoa and beat with a wooden spoon to mix.
6. Fold in the chocolate chips, pour into the lined tin and bake for about 45 minutes until risen and firm.
7. It will be slightly damp underneath the set top and that's the way you want it.
8. Remove to a wire rack and let cool in the tin. Once cool, get on with the icing.
For the Icing
1. Sieve the icing sugar.
2. In a heavy-based saucepan heat the butter, cocoa and ginger ale.
3. Once the butter's melted, whisk in the icing sugar.
4. Lift the chocolate gingerbread out of the tin and unwrap the paper.
5. Pour over the icing just to cover the top and cut into fat slabs when set.