Microwave onion pieces (reserve finely chopped onion), anchos, oil, sesame seeds, cocoa, garlic, cinnamon, and salt in bowl, stirring occasionally, until onion is softened, about 5 minutes. Transfer to Ace blender along with broth, tomatoes, raisins, and peanuts. Lock lid in place, then select Soup Program 2 (for creamy soups).
Once program has completed, carefully remove lid and stir in chicken. Let sit until heated through, about 2 minutes. Season with salt and pepper to taste. Serve filling on tortillas, topped with cilantro and finely chopped onion, passing lime wedges separately.