Preheat the oven 160C/325F/Gas 3. Grease and line a a loaf tin with non-stick baking parchment. Peel the bananas and mash together in a large mixing bowl. Add the softened butter and sugar and beat with an electric hand whisk until combined and smooth. Add the flour, rising agents, eggs and milk and continue to mix till you have a smooth cake mixture. Stir in the chocolate chips using a spoon and transfer the mixture into the prepared cake tin. Level the top using a palette knife and bake in the preheated oven for 45 minutes to an hour, or until well risen and golden-brown. Remove from the oven and allow to cool down completely in the cake tin.