Jalapenos are a small, dark green chili, normally 2 to 3 inches long and about 3/4 inches wide with a blunt tapered end. Jalapeno flavor varies from hot to very hot. Use 1 to 2 in this dish depending on your preference. Chilies can sting and irritate the skin; wear rubber gloves when handling chilies and do not touch eyes. Wash hands after handling.
Trim ends and remove any strings from beans; discard. Cut beans diagonally into thirds or quarters. Cut cauliflower into flowerettes. Cut onions into 1/2 inch pieces; keep white part and green tops of onions in separate piles. Chop garlic. Cut jalapeno lengthwise in half; remove stem and seeds. Cut jalapeno crosswise into thin slices.Heat the wok over high heat about 1 minute or until hot. Drizzle oil into the wok and heat 30 seconds. Add white part of onions, beans, cauliflowerettes, garlic, and jalapeno; stir fry until tender. Add carrots and 3/4 cup broth. Cover the wok and heat to a boil.Reduce heat to low and cook until carrots and beans are crisp tender.Combine remaining 1/4 cup broth, cornstarch, oyster sauce, sugar, and salt in a cup; stir until smooth. Stir into the wok. Cook until sauce boils and thickens. Stir in onion tops.Transfer to a serving dish. Garnish, if desired.