Ingredients:

5 med sized VERY ripe bananas
1tbsp butter
½ to 1 cup sugar (raw cane or Demerara recommended)
1 egg
½ tsp vanilla
1½ cups flour
1½ tsp bicarbonate of soda

Method:

Grease a standard loaf tin. Preheat the oven to 350F (180C).
Sift together the flour and bicarbonate of soda.
Mash the bananas. 
In a separate bowl, soften the butter with an electric mixer. 
Mix in the sugar and then add the beaten egg and vanilla.
Combine with mashed bananas.
Pour into the flour mixture and blend well.
Pour into greased baking tin and bake for 45 mins – 1 hour.