Preheat the oven to 175°C.
Butter and line an 8"x4" loaf tin.

Mash the bananas with a fork and stir in the butter (melted).

Whisk in the bicarbonate of soda, salt, sugar, egg and vanilla extract.
Mix in the flour and spices.

Chop up the nuts and chocolate into small pieces.
Combine into the batter.

Pour the batter into the loaf tin.

Combine all of the streusel topping ingredients in a bowl.
Place clumps of the topping on the top of the batter.

Bake for 60 minutes.
Take out and plunge a knife in 3 central regions of the loaf to test it is cooked all the way through.

Allow to rest in the loaf tin for 10 minutes.
Remove the loaf from the tin and rest on a cooling rack.