Blancmange (pronounced "bluh-MONGE") is a classic French dessert, similar to panna cotta or Bavarian cream, which today is made from milk (or cream) and sugar, and thickened with gelatin (or cornstarch), and prepared in a mold or dish.
When the blancmange is chilled and set, it can either be served in the dish or mold, or turned out from the mold beforehand.
But this is a lot different from the way blancmange used to be made.
Traditional Blancmange: A Rare Delicacy
The earliest version of blancmange in classical French cuisine was made with the milk of crushed almonds, rather than ordinary milk. And it was thickened with a substance called isinglass, which was derived from the swim bladders of European sturgeon (aka beluga, as in beluga caviar).
As such, it was considered a delicacy, since isinglass was expensive and difficult to obtain. Plus, preparing the blancmange required the dish to be submerged for several hours in crushed ice, which (other than during the wintertime) was only available to the very wealthiest people.
The word blancmange translates literally into "white food," from "blanc" (the French word for "white") and "mange" (the French word for "eat").
Indeed, the earliest blancmanges were prized for their whiteness and their smoothness. Which makes sense when one considers the fact that it was made by pounding blanched almonds into a fine paste using a mortar and pestle, then diluting with water and squeezing the the resulting almond milk through a cloth napkin.
Thus its whiteness was a function of how thoroughly the almond milk was extracted from the almonds; and its smoothness (always prized in French cuisine) a function of ensuring that no small bits of crushed almond made it through the squeezing process.
Additionally, traditional cooks used a combination of sweet and bitter almonds.
Sometimes they'd substitute hazelnuts or pistachios for almonds. Alternate flavorings including coffee, vanilla, chocolate, citrus and other fruits were also common.
Another important distinction: Blancmange was unquestionably a boozy dessert. Rum, brandy or flavored liqueurs were non-optional ingredients. A glance at a few modern blancmange recipes suggests that this practice has largely fallen by the wayside.
English Vs. French Blancmange
At some point in the recipe's evolution, isinglass was replaced by gelatin, which was much cheaper; and almond milk was replaced by ordinary milk (or cream) and flavored with almond extract.
This milk-based version is considered "English" blancmange, while the French version is still made using almond paste.
Note that the almond milk product that you can buy in supermarkets these days is a much weaker version of the almond milk made by pressing almonds, and it doesn't taste like almonds. So if you wanted to make a non-dairy blancmange, you could certainly use commercial almond milk, but you'd still have to flavor it with almond extract.
Finally, most modern recipes for blancmange call for thickening it with cornstarch rather than gelatin.