Set your oven to 180ºC / 350ºF . If you are using a thermofan oven set it slightly lower.  

Grease a 9 inch loaf tin.

In an electric mixer, beat the butter and sugar, until creamy.

In a separate bowl, beat the eggs with a fork,  and add well mashed bananas and vanilla essence .

Add this to the creamed butter and sugar mix. It will look a little curdled, but don't worry this will go once the flour is added.

Sieve the flour and baking powder into the mixture and beat for a minute or two until combined.

Add the baking soda (bicarb) to the boiling water and dissolve, then pour it into the mixture and beat until combined.

Pour mixture into the loaf tin and bake for 1 hour until golden brown.  Remember if you are using a thermofan oven you can reduce the temperature slightly, as it will cook quicker.  Keep watching it after 50 minutes so that it doesn't burn.  All ovens are different.

Allow to cool on a baking tray before serving with butter.

This recipe FREEZES well.