1⁄2 pound dried ancho chiles (about 20 chiles)
4 pounds bone-in country-style pork ribs (i.e., blade chops, not cut apart)
1 medium onion, chopped
1⁄2 teaspoon black pepper pinch ground cloves
2 tablespoons salt
1 head garlic, outer paper peeled off
2 sprigs fresh oregano or 1 teaspoon dried
2 sprigs fresh thyme or 1 teaspoon dried
1 stick canela (also known as Mexican or Ceylon cinnamon; a small stick of regular cinnamon may be substituted)
2 tablespoons cider vinegar
Make purée: Break off stems of chiles and shake out as many seeds as you can; discard stems and seeds. Cover chiles with water in a deep pan or pot (fill only about halfway). Bring to a boil, reduce heat, and simmer partially covered for about 30 minutes. Drain. Purée in batches in a blender (adding just enough water to aid the process). Strain purée through a strainer or chinois to remove remaining seeds and skin. (The purée may be made a day or so ahead and refrigerated; also freezes well.)
Cook ribs: Preheat oven to 350 degrees. On top of stove, place a 6-quart lidded Dutch oven or other heavy-bottomed ovenproof casserole over medium heat. Add pork ribs in batches and brown on both sides, about 5 minutes per side (you may cut them apart to fit in your cooking vessel). As pork begins to render its fat, add onion and brown it as well.
Add the chile purée, pepper, cloves, salt, garlic, oregano, thyme, canela, vinegar, and 1⁄2 cup water. Stir to distribute seasonings. Cover, place in oven, and roast until meat pulls away from bone and sauce is thickened, 2 to 2 1⁄2 hours.
Note: May be cooked on top of stove. Just peek under lid and add up to half a cup of water every 30 minutes, if needed, to prevent scorching. Serves 8.