Sift the flour into a large bowl, and add the sugar and mixed spice.
Cut the butter into small cubes and add to the flour mix. With cold hands (run them under a cold tap if needed) rub the butter and flour mix together until it's fine and sandy.
In a smaller bowl break the egg and whisk it, then pour into the flour and butter mix.
Add the raisins and mix well, pressing the mixture together tightly.
If it is a little dry add 1-2 tablespoons of milk, but no more.
Roll the dough into a ball and place on a surface dusted with flour.
Roll the dough out so it is approximately 1 cm thick.
Cut out each Welsh cake using a cookie cutter, and re-roll the leftover dough to cut again until it is all used up.
Rub your griddle/pan with a little butter and put on a medium heat.
Place the Welsh cakes in the pan and cook on each side for approximately 3-4 minutes until they're a deep golden colour, and cooked through.
Dust with caster sugar before serving.