Preheat the oven to 160C/325F/gas mark 3
Use two 23cm/9 inch springform tins.
Grease the tins. Sift the dry ingredients. Whisk the butter and sugar until light. Mix in the sour cream. Beat in the chopped nuts and the dry ingredients, taking care not to overbeat. Divide the mixture between the two tins and bake in the pre-heated oven for 40 minutes. When the cake starts to shrink away from the rides, remove from the oven and turn out on a wire rack.
Filling and Icing: Combine the sifted icing sugar and carob in bowl with butter. Stir in the combined coffee and water. Fill the cake, cover the top and coat the sides. Decorate with a few pecan nuts.
