Science in the Kitchen by E. E. Kellogg

3. Stir the grain continuously until it has set, but not at all

afterward. Grains are much more appetizing if, while properly softened, they can still be made to retain their original form. Stirring renders the preparation pasty, and destroys its appearance. Grains cooked in a double boiler will require no stirring, and there will be little danger of their being lumpy, underdone on top, and scorched at the bottom, as is so often the case when cooked in a single boiler.