The last experiment is the only one not easily performed in the school kitchen. The process can begin perhaps on one day, and be finished the next. If there is some apparatus that cooks at a low temperature, the practical difficulties may be overcome.
Vegetable, or "cream" soups.
These are of two classes: the purees (porridge), or thick soups, with vegetable pulp as the thickening material, and the cream soups, which are somewhat thinner, the juices of some vegetable giving the flavor.
Potato puree, or soup, is an example of the first; cream of tomato of the second. The line is not sharply drawn between the two in many cook books. Milk is an important ingredient in these soups, so that they are sometimes known as milk soups. Butter and flour are used in both, - the flour in the puree "binds " the mixture and makes it smoother; in the cream soup the flour is used for thickening as well.
Dried beans, peas, or lentils make a delicious puree, the secret of success being long slow cooking in some low temperature apparatus. They are brought to perfection in the Atkinson Cooker.