Preheat your oven to 190C / 375F / Gas mark 5 and very lightly grease your bundt pan with release spray or butter it.
Cream the butter an sugar together until it is light and fluffy.
Add the eggs one at a time beating between each addition.
Then add in the vanilla, mashed banana's and buttermilk and mix till fully incorporated into the batter.
Sieve, then gently fold in the baking powder, baking soda, salt and flour until just combined.
Then carefully fold in the chocolate chips and pour the batter into your bundt cake pan.
Place in the centre of your oven for 40 minutes.
My oven is a slow oven so check on the cake at 35 minutes, if a pick comes out clean then your cake is ready, if not then bake for another 5 minutes.
Once ready, take it out of the oven and allow it to sit in the cake pan for 20 to 30 minutes. Then turn it out on to a wire rack to fully cool down.
If you are making the icing drizzle, then mix your icing sugar with the water in a small bowl and drizzle over the top of the cooled cake.
As this is a moist cake, it will keep in an airtight tin at room temperature for up to 5 days. The un glazed cake can also be frozen for up to 2 months.