Mix the flour, baking powder and salt together in a large bowl.
Cut the cold butter into approximately 1cm/½ inch dice and toss into the flour. Rub the butter into the flour as if you were making a crumble.
Add the sugar, allspice and sultanas and mix into the flour, then beat the cold egg in a small jug before pouring into the bowl, and carry on mixing until you have a dough.
Wrap the dough and put in the fridge to rest for 15-20 minutes.
Roll out the dough on a lightly floured surface to a thickness of ½ cm / ¼ inch. Stamp out your Welsh Cakes.
Preheat a griddle or cast-iron frying skillet and cook the cakes for 3 to 4 minutes a side.
Transfer the Welsh Cakes to a platter and sprinkle generously with caster sugar. Serve immediately.
