Preheat your oven to 190°C/170°C(fan)/375°F/Gas 5.
In a small bowl, mash 3 Bananas.
In a large bowl, cream 170 g Butter, 170 g Caster sugar and 80 g Light brown sugar together until light and fluffy.
Add 3 Eggs and 1 teaspoon Vanilla extract and mix well.
Add the mashed banana and mix well.
In a separate bowl, mix together 370 g Plain flour, 0.5 tablespoon Ground cinnamon, 1 teaspoon Baking powder and 1 teaspoon Baking soda.
Add the flour mixture gradually to the large bowl, stirring well.
Gently stir in 75 g Dark chocolate chips and 300 ml Buttermilk.
Pour the mixture into a greased and lined 10x12 inch baking tray. Put into the oven for 50 minutes, until a knife or skewer comes out clear.
To make the frosting, mix together 300 g Cream cheese and 200 g Mascarpone. Then gradually add 250 g Icing sugar and 1 teaspoon Vanilla extract and mix well.
Once the cake it cooked, remove it from the oven and pan and put on a cooling rack and cool for at least an hour. Spread with the frosting and put in the fridge for a couple of hours for the frosting to set.
Notes
You could swap the dark chocolate chips for white chocolate chips.
Not a fan of cinnamon? Use ginger or nutmeg, or a mixture of the three.
You could make a chocolate cream frosting by swapping a little of the icing sugar for cocoa powder.
You can make these in to cupcakes by dividing the batter in to cupcake cases until half full and then baking for 22 minutes.
Feel free to get creative with extras like raisins, white chocolate chips or chopped pecans or walnuts.