Make the filling: Sear the chicken breasts on both sides in some oil and remove from pan. Saute onion until it starts to brown. Add garlic and taco seasonings (I used cumin, coriander, oregano, and smoked paprika, but feel free to use a store bought mix). Cook 1 minute. Add chipotle sauce and water and mix to combine everything. Add the chicken and allow sauce to simmer for about 25 minutes until chicken is cooked through. Remove chicken and chop/shred into small pieces. Return the chicken to the sauce and mix well.