Sieve flour, salt and cocoa into a bowl. Beat butter to a cream, add sugar and beat until light and fluffy. Add beaten eggs one at a time. Fold in flour mixture and add milk and vanilla. Turn into a greased baking dish.
Mix together sugar and cocoa for topping. Sprinkle over pudding, dot with pieces of butter and pour over hot water.
Bake for about 40 to 50 minutes in the preheated oven.