Preheat the oven to 180C/350F/gas mark 4
Use a 20cm/8 inch round cake tin.
Grease and line the cake tin. Cream together the butter and sugar until light and fluffy. Melt the carob bar or chips in a bowl over hot water. Leave to cool a little and then add to the cake mixture and stir until well blended. Stir in the yoghurt. Sift together the flour, baking powder and nutmeg. Add to the other ingredients and mix thoroughly.
Pour into the prepared cake tin and bake in the preheated oven for about 40 minutes or until a warm knife inserted into the centre comes out clean. Cool for a few minutes and then turn out on to a wire rack and leave until cold. Slice in half crossways and sandwich together with jam.
