Sift the flour into a bowl and add the diced butter.
Rub with your fingertips, or pulse in a food processor, until the mixture resembles breadcrumbs.
Add the sugar, sultanas and beaten egg and mix well to form a ball of dough, using a splash of milk if needed.
Roll the dough out on a floured board to a thickness of about 5mm/Â½in.
Cut into rounds with a 7.5â€“10cm/3-4in plain cutter.
Rub a bakestone or heavy iron griddle with butter, wipe away the excess and place on the hob until it is heated through.
Cook the Welsh cakes a few at a time for 2â€“3 minutes on each side, or until golden-brown.
Remove from the griddle and dust with caster sugar while still warm.