In a small bowl, combine the chicken broth, oyster sauce, soy sauce, vinegar, five spice powder and brown sugar. Set aside.
Heat a wok over medium-high heat. When hot, swirl in the cooking oil. Add in the onion and cook for 1 minute. Stir in the ground meat and cook for 2 minutes. Push aside the onion and ground beef to one side of the wok to create a small spot to fry the garlic. Add in the garlic and stir fry for a few seconds or until you begin smelling the garlic. Add in the bamboo shoots and mushrooms. Toss everything in the wok together.
Pour in the broth/soy sauce mixture and bring to a simmer. Cook for 2 minutes. Stir in the green onions. Serve the ground beef mixture over the noodles or rice.