1. Place chicken in a 5-6 quart greased slow cooker.
2. In medium bowl mix brown sugar, mustard, and salsa.
3. Pour mixture over chicken. Add water to cover chicken, if needed. Cook on low for 6-8 hours or high for 4 hours.
4. With 30 minutes of cook time remaining remove the lid and shred the chicken using two forks.
5. Add the beans, corn, and sour cream to the slow cooker and mix together with the chicken. Replace lid and cook for remaining 30 minutes.
6. Serve over rice with sour cream.
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