Cajeta is the Mexican version of what is widely known as dulce de leche throughout the broader Latin culture. The name derives from the Spanish word for "little box," which is how this confection was traditionally packaged. Much like its cousins, caramel and dulce de leche, this thick sauce of milk, baking soda and copious amounts of sugar, along with other more subtle flavorings like vanilla or cinnamon, can be found in numerous candies produced by and for the Mexican sweet tooth.
According to restaurateur Rick Bayless, who has written a half-dozen Mexican cookbooks as of 2011, 2 quarts of milk will produce 3 cups of cajeta. Bayless states that either goat or cow milk is acceptable — as well as a blend of the two. This is brought to a simmer with 2 cups of sugar and a cinnamon stick; others add vanilla extract for a more distinctive sweetness. Once it comes to a simmer, the pot is removed from the heat, and 0.5 teaspoon of baking soda is added. The liquid is then returned to a simmer and constantly stirred until a syrupy brownish color results.
As the syrup changes color, and thickens, the stirring should intensify, adding water if necessary to avoid burning. Then, when golden, cooks will strain cajeta before storing it in jars or other covered containers. It should not be refrigerated right away though, instead coming to room temperature before being cooled.
Cajeta differs from its relatives in a distinct but subtle ways. Caramel is a blend of cream, sugar and butter, which is simmered and stirred. Dulce de leche is just sweet condensed milk and a touch of salt, which is baked down to a browned glob, and then whisked and cooled before storage.
Like peanut butter or the iconic hazelnut spread known as Nutella®, it would not be odd to see cajeta eaten with a spoon, straight from the jar. It can be found stuffed into chocolate bars, spread over sweet breads, or poured over ice cream. It is also a popular dipping sauce for the Mexican fritter known as bunuelos.
Chefs often tinker with the standard recipe for cajeta, as they do with many other traditional dishes. Adding an alcohol like brandy or rum can make the expected more unique. Some also tinker with the goat's milk content; the more that is used, the more "barnyard" flavor in the final product. Using just cow's milk, by contrast, will eliminate that element completely.