Preheat the oven to 160 degrees Celsius. Grease a ring tin about 8cm deep and 20cm in diameter. Beat the butter and sugar until creamy. Add the eggs, one at a time, beating well between each addition. Add the flour and bicarbonate of soda and combine well. Add the bananas, sour cream and choc chips, and gently mix.
Pour into the prepared cake tin and bake for 40 - 45 minutes, or until the cake is firm to touch and a skewer inserted in the middle comes out clean.
Allow to cool slightly in the tin before turning onto a rack to cool completely. Dust with icing sugar to serve.
Recipe by Villiers Brown at http://villiersbrown.com/banana-and-chocolate-cake/