Preheat the oven to 180C/350F/Gas mark 4
Cream together the butter, sifted icing sugar and sour cream until light and fluffy. Stir in the sifted flour, custard powder and carob powder in 2 batches. Press the mixture together firmly with your hands. Knead on lightly floured surface until smooth. Cover and refrigerate for 30 minutes.
Roll the dough between sheets of greaseproof paper until 3mm thick. Cut 5cm rounds from the dough. Place about 3cm apart on greased baking trays. Bake for about 12 minutes or until lightly coloured; cool on trays.
Sandwich cookies with ½ level teaspoon carob cream. Spread the edges with a little more cream. Roll the edges in grated carob. Makes about 25.
Carob Cream: Combine the melted carob chips and butter. Cool to room temperature and then refrigerate for 10 minutes. Beat with a spoon until thick and spreadable.
