Heat oven to 180C/160C fan/gas 4. Butter a 2lb loaf tin and line the base and sides with baking parchment.
Cream the butter and sugar until light and fluffy, then slowly add the eggs with a little flour. Fold in the remaining flour, baking powder and bananas. Pour into the tin and bake for about 30 mins until a skewer comes out clean. Cool in the tin for 10 mins, then remove to a wire rack.
Mix the icing sugar with 2-3 tsp water to make a runny icing. Drizzle the icing across the top of the cake and decorate with banana chips.