Piloncillo is as minimally-processed as you can get your sugar, short of chewing it out of sugar cane yourself. It's the product of cane juice boiled down to a thick, crystalline syrup, usually poured into cone-shaped molds to harden (the name piloncillo derives from "pylon"). What you get is a sugar rife with impurities that puts plain old brown sugar to shame. Modern brown sugar is just purified white sugar with some molasses mixed in. This is the real deal.
'piloncillo' on Serious Eats
Piloncillo takes extremely well to spicy sauces flavored with dried chiles, as well as to the juicy tartness of tomatillos. This is my go-to chile sauce for recipes like tacos, enchiladas, and chilaquiles. Use it with or separately from the chicken that braises in it (the recipes makes extra sauce, which can be frozen and used later).