Bone And Skin Chicken; Cut Into Bite-Size Pieces. In A Shallow Bowl Or Large Resealable Plastic Bag, Combine 1/4 Cup Soy Sauce, Brown Sugar, Garlic And Cumin If Desired; Add Chicken. Cover Or Close Bag And Refrigerate For 4 Hours Or Overnight. Drain Chicken, Discarding Marinade. In A Large Skillet, Heat Oil Over Medium-High. Cook Chicken For 6-8 Minutes Or Until Juices Run Clear. Remove Chicken With A Slotted Spoon; Set Aside. Saute Celery In Drippings For 2 Minutes Or Until Crisp-Tender. Add Beans, Water Chestnuts And Mushrooms; Cook For 5 Minutes Or Until Heated Through. Add Chicken. Mix Water, Cornstarch And Remaining Soy Sauce; Stir Into Chicken Mixture. Bring To A Boil; Cook And Stir For 2 Minutes Or Until Thickened. Serve Over Rice.