Baked Alaska is basically an ice cream encased in some sort of hot casing (pastry crust or meringue). Early versions of this dessert consisted of ice cream encased in a piping hot pastry crust.
The later version consisting of ice cream on sponge cake covered with meringue and browned quickly in a hot oven.
The most common claim about the name "Baked Alaska" is that it was coined at Delmonico's, a restaurant in New York City, New York, USA, by its chef de cuisine Charles Ranhofer in 1867 to honor the acquisition by the United States of Alaska from the Russian Empire on March 10 that year.
The dish is also known as an "omelette à la norvégienne" or "Norwegian omelette", which similarly refers to the cold climate of Norway.
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.
The dish is made of ice cream placed in a pie dish lined with slices of sponge cake or Christmas pudding and topped with meringue. The entire dessert is then placed in an extremely hot oven for a brief time, long enough to firm and caramelize the meringue. The meringue is an effective thermal insulator, and the short cooking time prevents the heat from getting through to the ice cream and melting it.
Thin sheet sponge cake Make meringue of eggs and sugar as in Meringue I., cover a board with white paper, lay on sponge cake, turn ice cream on cake (which should extend one-half inch beyond cream), cover with meringue, and spread smoothly. Place on oven grate and brown quickly in hot oven. The board, paper, cake, and meringue are poor conductors of heat, and prevent the cream from melting. Slip from paper on ice cream platter.