1. Preheat the oven to 200˚C, gas mark 6. Line and grease a 900g loaf tin base.
2. With an electric whisk or stand alone mixer, beat the sugar with the eggs until pale and light. Add the mashed banana and continue beating until well mixed.
3. Add both flours, baking powder, bicarbonate of soda and the spices followed by the melted butter. Beat until incorporated and tip into the prepared tin.
4. Bake in the preheated oven for 50–60 minutes until risen and golden. (A skewer pushed into the middle should come out clean.)
5. Leave to cool in the tin for 10 minutes before removing and leaving to cool on a wire rack.
6. To make the frosting: beat the butter with the peanut butter, add the sifted icing sugar followed by the milk and beat until light and smooth.
7. Spread the icing all over the top of the cooled cake, scatter with the chopped nuts and serve with a good strong cup of tea.