Ice cream encased in some sort of hot casing (pastry crust or meringue). Also known as: ‘omelette a la norvegienne’, Norwegian omelette, omelette surprise, ‘glace au four’.
Baked Alaska consists of hard ice cream on a bed of sponge cake, the whole thing is then covered with uncooked meringue. This 'cake' is kept in the freezer until serving time, when it is placed in a very hot oven, just long enough to brown the meringue. Some brown it under a broiler, while I have seen others use a small blowtorch (propane) to brown the meringue. (Recipes: Classic Baked Alaska - Key Lime Baked Alaska)
Why the ice cream does not melt
Baked Alaska and similar desserts take advantage of the insulating properties of the trapped air in the cellular structure of foams (the meringue and sponge cake) which keeps the heat from reaching the ice cream. In the case of pastry crusts, the combination of air trapped in the layers of pastry and the air space between the pastry crust and the ice cream act as insulation, although not as well as the insulating provided by meringue.
Early versions of this dessert consisted of ice cream encased in a piping hot pastry crust. A guest of Thomas Jefferson at a White House dinner in 1802 described the dessert as "Ice-cream very good, crust wholly dried, crumbled into thin flakes."
The later version consisting of ice cream on sponge cake covered with meringue and browned quickly in a hot oven, is claimed as being created by many people, and popularized by many others. American physicist Benjamin Thompson (Count Rumford) claimed to have created it in 1804, after investigating the heat resistance of beaten egg whites. This was called omelette surprise or omelette a la norvegienne.
And then there is the story of it being passed on to the French in the mid 19th century when a Chinese delegation was visiting Paris. The Master-cook of the Chinese mission was staying at the Grand Hotel in 1866, and the French chef at the hotel (Balzac?) learned how to bake ice cream in a pastry crust in the oven from him.
The name Baked Alaska originated at Delmonico's Restaurant in New York City in 1876, and was created in honor of the newly acquired territory of Alaska. An Englishman (George Sala) who visited Delmonico's in the 1880s said:
"The 'Alaska' is a baked ice....The nucleus or core of the entremet is an ice cream. This is surrounded by an envelope of carefully whipped cream, which, just before the dainty dish is served, is popped into the oven, or is brought under the scorching influence of a red hot salamander."
It is was supposedly later popularized worldwide by Jean Giroix, chef in 1895 at the Hotel de Paris in Monte Carlo.