Preheat the oven to 350°F (175°C, 160° for fan ovens).
Grease a 14 cup Bundt pan well with butter. (If you only have a 12 cup Bundt pan, grease some cupcake pans or a small loaf pan or two.) Dust the pan(s) with flour, tapping out any excess.
Sift the flour, baking powder, baking soda, salt, ginger, cinnamon, nutmeg and cloves into a large bowl. Set aside.
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 at medium speed.
Add the eggs, one at a time, with a tablespoon of the flour mixture for each, 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 remaining flour mixture alternately with the buttermilk (2 additions of each, starting with the flour), beating until just combined.
Beat in the pumpkin puree, blending thoroughly..
Pour the batter into the Bundt pan until it is just less than three-quarters full. (If you have leftover batter, consider making some cupcakes or even a small loaf cake.)
Bake the cake for about 45 to 55 minutes or until a skewer inserted in the centre comes out clean. Ideally, the outside should be beginning to turn a light golden brown colour.
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 or lemon juice, until a smooth, drizzle-able consistency is reached. (Go carefully, as you may need more or less liquid.)
Drizzle the glaze over the cooled cake.
Sprinkle with the chopped crystallised ginger, if using.
Allow the glaze to dry before slicing and serving.