Crockpot Cranberry Chicken

I found this on the Cooking Light Message Board. Original Source is unknown.

1 small onion, thinly sliced
1 cup fresh or frozen (unthawed) cranberries
12 skinless, boneless chicken thgihs (about 2 1/4 lbs. total) (I used boneless, skinless breasts)
1/4 cup catsup
2 tablespoons firmly packed brown sugar
1 teaspoon dry mustard
2 teaspoons cider vinegar 1 1/2 tablespoons cornstarch blended w/2 tablespoons cold water
salt

In a 3-quart or larger electric slow cooker, combine onion, cranberries. Arrange chicken on top. In small bowl, mix catsup, sugar, mustard and vinegar and pour over chicken. Cover. Cook at low setting until chicken is very tender when pierced (6 1/2 to 7 1/2 hours).

Lift out chicken when done, blend cornstarch mixture into cooking liquid. Increase cooker heat setting to high; cover and cook, stirring 2 or 3 times until sauce thickens (10 to 15 more minutes). Season to taste with salt; pour over chicken. Makes 6 servings.