Pineapple Chicken

This recipe is one I received from my mother-in-law, but I've tweaked it a little for crock pot cooking.

Pineapple Chicken
4 chicken breasts, diced
1 large onion, diced
4-5 celery stalks, sliced
2 green peppers, diced
2 cans pineapple chunks, including juices
1/2 cup brown sugar
1/4 cup soy sauce
1 T ginger
salt and pepper to taste.

Combine everything in crock pot. Cook on low for 6 hours, high for 4. About 30 minutes before serving, combine 1/4 cup cornstarch with a little water, whisking well to remove lumps, then add cornstarch to chicken mixture. Whisk well and cook until thickened. (If you've had your crock pot on low, this would be a good time to turn it up to high.) Serve over rice.