Step 1

Place chicken and broth in heavy large pot. Bring to boil. Reduce heat to medium-low, partially cover pot and simmer until chicken is cooked, about 30 minutes. Cool chicken in broth. Strain broth and spoon off fat; reserve broth. Remove chicken skin and bones; discard. Shred chicken coarsely; transfer to large bowl.

Step 2

Heat 3 tablespoons oil in large saucepan over medium-low heat. Add 1 cup onion, garlic, oregano, cumin and cinnamon. Cover. Cook until onion is almost tender, stirring occasionally, about 10 minutes. Mix in chili powder and flour; stir 3 minutes. Gradually whisk in 4 1/2 cups broth. Increase heat to medium-high. Boil until reduced to 3 cups, stirring occasionally, about 35 minutes. Remove from heat. Whisk in chocolate; season with salt and pepper. Cool.

Step 3

Heat 1 tablespoon oil in medium skillet over medium heat. Add 1 tortilla and cook until just pliable, about 20 seconds per side. Transfer to paper-towel-lined baking sheet. Repeat with remaining tortillas, adding oil as needed.

Step 4

Spread 1/3 cup sauce in each of two 13 x 9 x 2-inch glass baking dishes. Mix 1 cup sauce into chicken. Arrange 8 tortillas on work surface. Spoon 3 tablespoons cheese, 1 tablespoon olives, 1 tablespoon onion and 1/4 cup chicken over center of each. Roll up tortillas. Arrange seam side down in 1 prepared dish. Repeat with remaining tortillas, 1 1/2 cups cheese, olives, onion and chicken. (Can be made 1 day ahead. Cover sauce and enchiladas separately; chill.)

Step 5

Preheat oven to 375°F. Top enchiladas with remaining sauce, then sprinkle with remaining cheese. Cover with foil; bake 20 minutes (30 minutes if chilled). Remove foil and bake until sauce bubbles, about 10 minutes. Let stand 10 minutes.