Use small paper cases to line the fairy cake tins. Preheat the oven to 180C / 350F / Gas 4.
In a large bowl sift together the flour, baking powder, bicarbonate of soda, salt and spices. Stir in the sugar and make a well in the centre.
Use a jug to mix together the eggs, melted butter, soured cream, milk and vanilla extract. Pour into the well and mix quickly just until the mixture comes together. Take care not to over-mix, it should still be slightly lumpy and not smooth. Quickly fold in the blueberries and spoon into the paper cases. Sprinkle the demerara sugar over the tops and bake for 20 minutes or until golden on top.
Stir the creme de cassis or Ribena into the clotted cream and serve with the fairy cakes.