Preheat the oven to 160C/325F/gas mark 3
Use a deep 20cm/8 inch loose bottom cake tin.
Grease and line the cake tin. Sift the white flour, spice, baking powder and bicarb. into a large bowl and stir in the wholemeal flour. Rub in the butter until the mixture resembles fine breadcrumbs and stir in the sugar and sultanas.
Make a well in the centre and gradually pour in the sour cream and milk. Beat gently until well mixed and of a soft dropping consistency, adding more milk if necessary. Turn the mixture into the prepared tin and level the surface. Roughly crush the sugar cubes and scatter over the cake. Bake in the oven for about 1 hour 40 minutes or until a warm knife inserted into the centre comes out clean. Turn out to cool on a wire rack.
