Growing up in urban areas of northern Mexico makes for pretty lousy food memories, as far as traditional eats are concerned. Having parents that were born elsewhere doesn't help either as far as my exposure to what the local sweets are. However, I did get to know a few of the sweets of the region. Like Jamoncillos, Cocadas and the most famous "sweet" of the region: Pan de Pulque.
Jamoncillos and Cocadas share two ingredients that could be considered staples in pretty much every region of Mexico: Milk and Sugar. Wherever you go in Mexico you're bound to find sweets based on custards, curdled milk or more commonly caramelized milk. On a more modern note, condensed milk has also made a place for itself in the sweet pantry of our kitchens.
In the 2003 movie "Politiki Kouzina" (A touch of Spice), the main character reflects on milk and sugar. He mentions having seen many seniors walking around with boxes of sweets based on these ingredients, which are, ironically, the first flavors we taste.
One very popular sweet combination, and one that many Mexicans have eaten regardless of their region is the Galletas Marías and Cajeta. The former being a very popular biscuit, the latter, our version of Dulce de Leche (made from goat's milk).
Taking that idea and this one from Linda, I wonder how people would react to a new, elegant version of the childhood staple. How about Galletas Marías and Lemon??