Break broccoli into florets, peel stems and cut into 1-inch pieces. Bring 3/4 cup broth to boil in medium saucepan. Add broccoli stems, cover and cook until crisp-tender, 3 to 4 minutes. Drain, reserving 1/2 cup broth. Heat oil in wok or large skillet. Add ginger, onion and garlic and stir- fry 1 minute. Add broccoli stems and florets and stir-fry 2 minutes. Add oyster sauce, sugar and 1/2 cup broth and stir-fry 2 minutes. For thicker sauce, stir in cornstarch dissolved in 2 teaspoons broth and cook briefly.