1. Cream butter, sugar and vanilla essence until light and fluffy.
2. Add eggs, one at a time, beating well after each addition.
3. Sift flour with salt and fold in alternately with milk.
4. Grease a 6 or 7 cup pudding basin and spread jam in the base.
5. Spoon in pudding batter, cover basin with a square of buttered aluminium foil and place lid on top.
6. If using a china basin, cover with two layers of buttered greaseproof paper, top with a layer of foil and tie on securely under rim of basin with string.
7. Place a round wire cake rack or invert a saucer in the base of a large saucepan of boiling water.
8. Place pudding on this and make sure water comes half way up sides of basin.
9. If not, add boiling water.
10. Cover pan and steam for 2 hours.
11. During cooking, add boiling water to pan when necessary.
12. Invert onto serving dish and serve hot or warm with custard or cream.