Boil the chicken for 25 minutes or until cooked. Set aside.
In a blender combine the tomatoes, chipotle sauce, garlic, cumin, pepper, salt and add 9 ounces of water and blend for a few seconds.
In a saucepan add the vegetable oil and onions and cook for 3 minutes or until the onions turn golden.
Add the chipotle mixture and the chicken to the saucepan with the onions and cook over medium heat 15 minutes.