Oven-Braised Pork Belly with Sweet Onions, Apples, and Mexican Chocolate

What makes an onion sweet? Sulfur is what gives onions their pungent, sharp flavor. Grown in sulfur-poor soil, sweet onions have half—or even less than half—the usual amount of sulfur, which means their natural sugars can shine. Any sweet onion variety, such as California Sweet, Vidalia, Walla Walla, or Maui, can be used for this recipe. This tender, flavorful pork belly can be diced and used as a taco filling along with a little of its braising liquid, cut into large dice for a casserole,