Trim fat from steak; cut steak diagonally across grain into thin slices. Combine steak and cornstarch. Heat oil in a large nonstick skillet over medium-high heat until hot. Add steak mixture; sauté 3 minutes. Stir in ginger and garlic; cook 10 seconds. Stir in carrots and next 6 ingredients (carrots through water chestnuts); cover and cook 4 minutes. Stir in bok choy; cover and cook for 2 minutes. Serve with rice.