Preparation

• In a 5- to 6-quart Dutch oven or other heavy-duty pot, heat 2 Tbs. of the oil over medium heat. Add the ancho chiles, garlic, and onion, and cook, stirring frequently, until the onion and garlic have browned and the chiles are toasted and aromatic, 5 to 6 minutes. Scrape the mixture into a blender and set the pot aside.
• To the blender, add 1-1/2 cups of the broth, the tomatoes and their juice, the bread, chipotle chiles, peanuts, cinnamon, and allspice; purée until very smooth, 2 to 3 minutes. Rub a drop of the purée between your fingers; if it doesn’t feel smooth, transfer to a medium-mesh strainer set over a medium bowl and press the mixture through with a spatula.
• Heat the remaining 2 Tbs. oil in the pot over medium-high heat. When the oil is hot, add the sauce. Cook, stirring constantly, until reduced by two-thirds and darkened to a thick, rusty orange paste (about the consistency of tomato paste), 15 to 20 minutes.
• Stir in the remaining 2 cups broth and the chocolate. Partially cover the pot, reduce the heat to low, and simmer, stirring occasionally, until the sauce thickens to a heavy cream consistency, 30 to 45 minutes. Stir in 2 tsp. salt and the sugar, adding more of both to taste.
• Position a rack in the center of the oven and heat the oven to 350°F. Put the chicken in a 9×13-inch baking dish. Add the sauce, covering the chicken. Bake, uncovered, until the chicken is just cooked through (165°F), 35 to 40 minutes.
• Transfer the chicken to plates or a platter, scraping the sauce on the chicken back into the baking dish as you do. Whisk the sauce until well combined and spoon it back over the chicken. Top with the chopped peanuts and parsley, if using, and serve.

Make Ahead Tips

The sauce may be made 1 or 2 days ahead. Cover and refrigerate; reheat gently before using.