Cut beef with the grain into 2-inch strips, then cut across the grain into ¼-inch pieces, or use pre-cut beef strips for stir fry.
Add beef to a bowl with vegetable oil, cornstarch and soy sauce. Stir to coat, marinate for 10 minutes.
Peel and cut onion in half, trim both ends. With cut end toward you, cut each into ½-inch strips across onion. Cut celery into ½" pieces and asparagus into thirds. Set aside.
In small bowl, whisk together beef broth, bean paste, vinegar, soy sauce, garlic, ginger, red pepper flakes and sesame oil. Set aside.
Heat a wok over high heat. Once hot, add 2 tablespoons oil and stir fry the beef. Be sure to break meat apart into strips if stuck together. Continue stir frying for 3 minutes, tossing occasionally until beef is no longer pink. Remove from wok and set aside.
Add the onion and stir fry for 3 minutes. Add the celery and cook another 3 minutes. Add the asparagus, sauce mixture and beef back to the wok and stir fry for 4 minutes.
Serve as is, over noodles or with steamed rice. Garnish with toasted sesame seeds and cilantro sprigs (optional).