Preheat the oven to 180C/350F/gas mark 4
Use a 20cm/8 inch round deep cake tin.
Grease and line the tin. Cream the butter, essence and sugar. Mash the banana and stir in half with half the sour cream and half the dry ingredients. Stir in the remaining banana, sour cream and dry ingredients. Spread into the tin. Bake for l 1/4 hours. Allow to cool for 10 mins. before turning out on a wire rack. Carob icing. Beat the cream cheese and butter. Gradually beat in half the sifted icing sugar, the carob then the remaining icing sugar. Beat until thick. Spread over the cold cake.
