Grease and line with baking paper a 10cm x 22cm baking loaf pan.
Pre-heat a fan forced oven to 180°C (350°F).
In a large bowl, add brown sugar, self-raising flour, cocoa powder and dark choc chips. Stir to fully combined.
In a separate bowl, add buttermilk, melted butter, eggs and mashed bananas. Stir to fully combine.
Add banana mixture to the flour mixture and using a spoon stir to combine.
Pour the mixture into the baking loaf pan and smooth the surface.
Bake in oven for about 50 minutes or until a skewer inserted into the centre comes out clean.
Remove from oven and allow to cool in pan for about 10 minutes before turning out onto a wire rack to cool completely.
Cookies & Cream Icing
In a medium bowl, add softened butter and using an electric mixer, beat until pale and creamy.
Gradually add icing sugar and continue beating until fully combined and creamy.
Add milk and beat until fully combined.
Add melted white chocolate and continue beating until fully combined. Note: to melt white chocolate, place in a glass bowl, set microwave to 50% power and cook at 30 second intervals until melted. Check and stir between each 30 second interval.
Spread mixture over the cooled banana bread and topped with crushed Oreo pieces.