Chicken Taco Soup

1 chopped onion
1 (16.5 oz.) can chili beans
1 (15 oz.) can black beans
1 (15 oz.) can corn
1 (8 oz.) can tomato sauce
2 (10 oz.) cans diced tomatoes w/green chilies
1 packet taco seasoning
3 whole chicken breasts

Place ingredients in slow cooker and stir. Place chicken on top, pressing down until just covered by ingredients. Cook for 5 hours. Remove chicken and shred. Put chicken back into mixture and cook another hour. Top with dollop of sour cream, cheese and crushed tortilla chips prior to serving.