Mix flour with suet, fruit, sugar, cinnamon and soda. Stir in enough milk to make a soft batter. Dip a pudding cloth (cheesecloth) into boiling water, sink it in a basin large enough to hold the batter. Dredge it lightly with flour and spoon in the batter. Draw the fullness of the cloth together evenly, then tie it tightly with string, but leave enough room for the dumpling to swell. Place a saucer or plate in the bottom of a large saucepan. Lift the dumpling into the pan. Pour in enough boiling water to cover. Simmer for a full 2 hours, then untie. Turn out carefully onto a hot serving dish. Dredge with castor sugar. Serve with hot custard sauce. Yields 4 to 6 servings.
For the hot custard sauce, we usually use Byrd's Custard. If you have the availability of British goods in your area, they should have Byrd's custard. It comes in a large tin, like a container of powdered chocolate for chocolate milk. Just follow the directions to make a custard, only dilute it a little more to make it sauce-like.