Combine the first 8 ingredients together in a slowcooker. Top with the chicken breasts. Cook on low for 6 hours, or high for 4 hours.
Thirty minutes before serving, remove the chicken breasts & shred with 2 forks. Stir the shredded chicken into the mixture in the crockpot. Cook for 30 minutes. Serve with cilantro and sour cream if desired.