Trim outer leaves and tough ends from broccoli. Cut stalks and flowerets into 2" lengths, then slice thin, lengthwise. Heat oil in large wok or skillet; add broccoli and cook stirring constantly until broccoli turns a bright green. Add water and soy sauce. Stir in celery and water chestnuts. Heat to boiling, cover. Steam 5 minutes.

While broccoli cooks, heat sesame seeds over low heat in small heavy skillet. Shake pan constantly, just until lightly toasted; stir into broccoli mixture. Place in bowl and serve with more soy sauce to sprinkle over top.