Question: Why is it necessary to use a double boiler while making pudding?
About the article "Pudding", section "Creamy puddings".

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The second and newer type of pudding consists of sugar, milk, and a thickening agent such as cornstarch, gelatin, eggs, rice or tapioca to create a sweet, creamy dessert.
These puddings are made either by simmering on top of the stove in a saucepan or double boiler or by baking in an oven, often in a bain-marie.
These puddings are easily scorched on the fire, which is why a double boiler is often used; microwave ovens are also now often used to avoid this problem and to reduce stirring.
Creamy puddings are typically served chilled, but a few, such as zabaglione and rice pudding, may be served warm.
Instant puddings do not require boiling and can therefore be prepared more quickly.
This pudding terminology is common in North America and some European countries such as the Netherlands, whilst in Britain egg-thickened puddings are considered custards and starch-thickened puddings called blancmange.
When wheat flour began to come into common use for making cakes and puddings, cooks in the north of England devised a means of making use of the fat that dropped into the dripping pan to cook a batter pudding while the meat roasted in the oven.
In 1737, a recipe for 'a dripping pudding' was published in "The Whole Duty of a Woman":Similar instructions were published in 1747 in "The Art of Cookery made Plain and Easy" by Hannah Glasse under the title of 'Yorkshire pudding'.
It was she who re-invented and renamed the original version, called Dripping Pudding, which had been cooked in England for centuries, although these puddings were much flatter than the puffy versions known today.
The Yorkshire pudding is meant to rise in a correctly executed preparation.
A 2008 ruling by the Royal Society of Chemistry has it that "A Yorkshire pudding isn't a Yorkshire pudding if it is less than four inches tall".
The Yorkshire pudding is a staple of the British Sunday lunch and in some cases is eaten as a separate course prior to the main meat dish.
This was the traditional method of eating the pudding and is still common in parts of Yorkshire today.
Because the rich gravy from the roast meat drippings was used up with the first course, the main meat and vegetable course was often served with a parsley or white sauce.
Traditionally, though less so now, the Yorkshire Pudding could be served as a sweet, with sugar, golden syrup, jam, or even with orange juice as a sauce.
It is often claimed that the purpose of the dish was to provide a cheap way to fill the diners, thus stretching a lesser amount of the more expensive ingredients as the Yorkshire pudding was traditionally served first. 
Christmas pudding is a type of pudding traditionally served on Christmas Day (December 25) as part of the Christmas dinner.
It has its origins in medieval England, and is sometimes known as plum pudding or Christmas Pudding or just "pud", though this can also refer to other kinds of boiled pudding involving dried fruit.
Despite the name "plum pudding," the pudding contains no actual plums due to the pre-Victorian use of the word "plums" as a term for raisins.
The pudding is composed of many dried fruits held together by egg and suet, sometimes moistened by treacle or molasses and flavoured with cinnamon, nutmeg, cloves, ginger, and other spices.
The pudding is aged for a month or even a year; the high alcohol content of the pudding prevents it from spoiling during this time. 
Persimmon pudding is a traditional American dessert made with persimmons.
Although American, persimmon pudding is similar to traditional English dessert puddings, such as Christmas pudding or quince pudding.
This style of pudding is generally either steamed or cooked in an oven with a water bath, or bain-marie.
These methods of cooking ensure the pudding remains moist and does not dry out or form a crust unlike the sweet but crusted persimmon bread.
The pudding is often served with ice cream, crème anglaise, whipped cream, apple sauce, or brandy butter.
It is best served warm, although it can be served cold as well.
Persimmon pudding lasts quite a while when refrigerated, and may be made in large batches to be served over the course of several days.
As the pudding ages the various individual flavors mellow and blend together.
In the U.S. state of Indiana, it is considered one of two legendary local dishes; the other being sugar cream pie. 
Pudding is usually a dessert, but it can also be a savory dish.
In the United Kingdom and most Commonwealth countries, "pudding" can be used to describe both sweet and savory dishes.
However, unless qualified, the term in everyday usage typically denotes a dessert.
In the United States and Canada, "pudding" characteristically denotes a sweet milk-based dessert similar in consistency to egg-based custards, instant custards or a mousse.
A  Ábrystir  Almond jelly  Ashure  Asida B  Bakewell pudding  Banana pudding  Bánh chuối  Bazeen  Bebinca  Blancmange  Blodpalt  Bread Pudding  Brown Betty (dessert) C  Capirotada  Carrot pudding  Chè  Cheese pudding  Chireta  Chocolate biscuit pudding  Chocolate pudding  Christmas pudding  Clootie  Cottage Pudding D  Diplomat pudding  Dock pudding  Drisheen  Dutch baby pancake F  Figgy duff (pudding)  Flummadiddle  Flummery  Fruit pudding  Frumenty G  Giga Pudding  Goody (dessert)  Götterspeise  Vincent Gruppuso H  Hasty pudding  Haupia  Herrencreme J  Junket (dessert) K  Kačamak  Kalamai (dessert)  Kirschenmichel  Kulolo  Kutia M  Malva Pudding  Mango pudding  Moin moin  Monmouth Pudding P  Panna cotta  Persimmon pudding  Pistachio pudding  Po'e  Put chai ko R  Rag pudding  Red pudding  Rice pudding  Rødgrød  Rømmegrøt  Rožata S  Sago pudding  Scrapple  Semolina pudding T  Tapioca pudding  Tembleque  Tiết canh W  Welf pudding