Cream butter, add molasses and mix. Add the hot water and stir well.
Sift the soda and flour together and beat well into the butter mixture. Fold in the raisins.
Place the batter in a greased steaming can and steam 3 hours. (Empty baking-powder tins with tightly fitting lids make good steaming cans. Fill 2/3 full. Place on a rack in a heavy kettle with an inch of boiling water in the bottom. Cover the kettle.)
Serve warm or cold with a sauce.