Preheat the oven to 350°F (180°C, 170° for fan ovens).
Grease a 14 cup Bundt pan with a little butter. Sprinkle with flour. Tap out excess flour. Set aside.
Sift the flour, baking powder, baking soda, salt, ginger, cinnamon, nutmeg and cloves into a large bowl. Set aside.
Using medium speed, beat the butter and brown sugar together in the large bowl of an electric mixer fitted with a paddle attachment. This will take 2 or 3 minutes.
Add the eggs, one at a time, beating well after each addition.
Don't forget to scrape down the bowl from time to time.
Reduce the mixer speed to low.
Add the flour alternately with the buttermilk (2 additions of each, starting with the flour), beating until just combined.
Beat in the pumpkin puree.
Pour the batter into the Bundt pan you prepared earlier.
Bake the cake for about 55 minutes. The outside should be beginning to turn a light golden brown colour, and a skewer inserted in the centre should come out clean.
Remove the Bundt pan from the oven and set it on a wire rack to cool.
After half an hour, carefully turn the cake out of the Bundt pan and on to the wire rack to cool completely.
For the glaze, mix the icing sugar gradually with the water, until a smooth, drizzle-able consistency is reached. (Go carefully, as you may need more or less water.)
Drizzle the glaze over the cooled cake.
Sprinkle with the chopped crystallised ginger, if using.
Allow the glaze to dry before slicing and serving.