In a medium pot, heat your olive oil over medium high heat and saute your onion until the onion is transparent, 3-4 minutes. Add in the garlic and saute just another minute.

Add your chicken broth, chicken breasts, prepared tomatoes, salt and pepper to the pot. Bring everything to a boil then cover and reduce heat to low. Simmer until the chicken is cooked through, about 30-40 minutes.

Once the chicken is cooked, remove it from the pot and shred it. Set aside.

Use a slotted spoon to remove all the tomatoes and onions from the pot and add them into a blender with ¾ cup of your boiling liquid. Blend until smooth. Discard the remaining liquid from the pot and return the pot to medium heat.

Add the chicken and blended mixture to the pot along with your oregano, chipotle pepper, and cumin. Cook the chicken in the sauce, stirring continuously for about 5 minutes. The chicken should be evenly coated and the sauce will reduce slightly. You can add additional salt and pepper to taste.