Preheat the oven to 190C/375F/gas mark 5
Use two 20cm/8 inch cake tins.
Grease and line the cake tins. Cream together the butter and sugar until the mixture is light in colour and texture. Gradually beat in the sour cream. Sieve together the dry ingredients and fold them into the mixture. Divide the mixture equally between the tins. Bake for 30-35 minutes, until cooked. Turn out on to a wire tray to cool.
Make the filling by mixing the carob with 2 tbs. of boiling water to a smooth paste. Allow to cool. Beat together the butter, sieved icing sugar and essence, until light and fluffy. Beat in the carob. Slice the cake in half and then sandwich the halves together with the filling.
For the icing, melt the carob chips or bar carefully over water. Make the carob powder into a paste with water as before and mix with the melted bar. Slowly whisk in the cream until smooth and thickened. Spread the icing evenly over the cake with a cake slice. Serve hot with whipped cream or ice-cream.
