Mix all dry ingredients thoroughly in a large bowl.
Add wet ingredients and mix well by hand.
Divide mixture into two greased 1.5 litre heatproof bowls and smooth the surface.
Cover bowls with greaseproof paper and foil, then tie securely with string to create a handle.
Rest the puddings in a cool place overnight before cooking.
Place bowls on a trivet in a large pan and add boiling water to reach halfway up the sides.
Cover pan and boil for seven hours, replenishing water as needed.
Cool the puddings, remove wrappings, and replace with clean paper and foil.
Store in a cool place and steam for two hours to reheat before serving.