Cream the butter and sugar in a bowl until fluffy and almost white. Gradually add the beaten eggs, mixing vigorously. Sift the flour and baking powder into a bowl.
Gradually incorporate the flour into the mixture as lightly as possible, keeping to a dropping consistency by adding a little milk.
Place in a greased 1.2 litre pudding mold, and cover with greaseproof paper and secure with string. Place basin in a large pot and fill with water until 2/3rd of the pudding mold is covered with water.
Cover pot and steam the pudding for 1-1½ hours - checking every so often to see if water needs topping up.
Remove from pot, take off paper and run a spatula around the edge of the bowl to release the pudding.