Preheat the oven to 170°C/325°F/Gas 3.
Lightly grease and base line a 900g/2lb loaf tin.
Melt the butter in the microwave
Combine the butter and sugar and mix well
Beat the eggs, add to the bowl and mix well until mixture is smooth
Add the milk and mix well
Mash the bananas into the mixture and mix well
Sieve the flour and baking powder and gently stir into the mixture until it is just combined
Fold in the chopped walnuts or chocolate chips
Transfer to the prepared tin and bake in a central oven position for about 50 minutes until well risen and a knife gently pressed into the bread comes out clean. You can cover it with tinfoil after 25 minutes to stop it browning too much on top if needed
Allow to rest in tin for about 10 minutes then turn onto a wire tray to cool.
When cold, wrap in greaseproof paper and tinfoil.