Cream the butter and sugar in a bowl. Beat in the eggs, one at a time.
Sift the flour, baking powder and salt together, and fold into the mixture, adding just enough milk to give a dropping consistency.
Butter a 1.2-litre/2pt pudding basin, then pour the syrup into the bottom. Spoon in the batter to fill the basin. Cover the top with a round of buttered baking parchment, and secure pleated foil over that with string.
Stand in a pan of simmering water with a lid on, and steam for 1 1⁄2 hours, topping up with boiling water when necessary. Invert the pudding onto a serving plate. Serve hot.