Preheat oven to 160C (350F) fan-forced.
Generously butter a bundt tin, then dust it with flour, tapping to shake out the excess. I found it easier to sift the flour onto the tin.
In a large mixing bowl, whisk together the flour, sugar, cocoa, baking powder, baking soda, spices, and salt.
In a second bowl, whisk together the buttermilk, pumpkin and brown sugar until smooth then whisk in the whole egg and the egg white.
Finally, add the oil, corn syrup and vanilla and whisk until smooth.
Make a well in the dry ingredients and carefully fold in the wet ingredients until just combined.
Spread the batter into the tin and smooth out the top.
Bake the cake for 1h to 1 hour 15 minutes or until a cake tester inserted in the middle comes out clean.
Leave it to rest in the tin for 15 minutes and then cross your fingers and turn it out onto a wire rack to cool completely.
To make the drizzles, divide the icing sugar into three bowls.
To one, add the cocoa and to another add the pumpkin puree.
Add just enough water to each one to make it into a drizzle then when the cake is cool, drizzle them over the top and leave them to set.