Combine chicken, water, 1/4 onion, 2 garlic cloves and 1 1/2 teaspoons salt in a large pot.  Bring to a boil over medium heat. Reduce heat to medium-low, cover and simmer for 1 hour. Remove from heat and set aside.

Heat 2 tablespoons vegetable oil in a large pan over medium heat. Fry dry chile skins in batches; about 3 minutes or until skins are soft. Do not burn. Transfer to a large bowl and add 7 1/2 cups of broth from the boiled chicken. Add the chocolate tablet and remaining 1 teaspoon salt.

Heat 1 tablespoon of oil over medium heat in large frying pan previously used to fry chile skins. Add remaining 1/4 onion, remaining garlic cloves, peanuts, pecans, raisins, tomato halves and banana to frying pan.  Fry for 20 minutes stirring frequently; Do not burn. Transfer all fried ingredients and toasted sesame seeds to the large bowl where chile skins are soaking. Soak all ingredients for 40 minutes more or until chile skins are very soft and chocolate tablet has completely dissolved.

Transfer all soaked ingredients to blender container, blend until smooth. Heat remaining tablespoon of oil in a large saucepan over medium heat.  Pour in sauce and stir in sugar.  Continue stirring until sauce comes to a simmer; about 15 minutes.  Turn off heat, cover and keep warm.

Chop chicken into large pieces and add to sauce.  Serve.  Garnish with toasted sesame seeds.