The success of this cake is in the bananas — they must be ripe, over-ripe even, to ensure the cake is moist — and in the rich, buttery chocolate icing, lots of it.
Heat oven to 180C and grease and line a 20cm cake tin.
Cream butter and sugar until really light and fluffy, then beat in eggs, one at a time. Warm the milk then stir the soda into it. Add to the creamed mixture along with the mashed banana.
Sift in flour and baking powder and fold through gently.
Pour into prepared tin and bake for 50 minutes or until cake springs back when lightly pushed. Rest in tin for 5 minutes before turning on to a rack to cool before icing.
To make the icing, place all ingredients into a bowl and pour in approx. 1 Tbsp boiling water. Beat until smooth, adding water a little at a time until smooth and spreadable.