First place the currants in a small bowl and spoon over the rum, leaving them to soak for at least an hour.
Sift the flours, baking powder and sea salt into a large bowl.
Then stir in the suet, sugar, soaked currants (without the excess liquid), mixed peel and spices.
Pour in just enough milk to make soft dough, mixing together with your hands.
Shape the dough into a thick log and loosely wrap in muslin or cheesecloth, securing the ends with string.
Then wrap in foil.
Place the Spotted Dick in a large saucepan, pour boiling water all around the spotted dick until it has submerged and bring up to a boil. Turn the heat down to simmer, put the lid on and leave to cook for two hours.
Remove the Spotted Dick carefully from the water and serve immediately with lashings of custard.