In a large skillet or wok, heat 1 tablespoon of vegetable oil over medium-high heat. Add the diced onion and celery, and sauté until they begin to soften, about 2-3 minutes.

Add the hamburger to the skillet and cook until browned, breaking it up into small pieces as it cooks.

Once the meat is browned and no longer pink, add the salt, pepper, and 1 1/2 cups of water to the skillet. Cover and simmer for 20 minutes to allow the flavors to meld.

After 20 minutes, stir in the drained bean sprouts and chopped green cabbage. Continue to simmer for an additional 5 minutes.

In a small bowl, mix together the cornstarch and 2 tablespoons of water until smooth. Add the soy sauce, oyster sauce, beef gravy (or molasses), and sugar to the cornstarch mixture, and stir until well combined.

Pour the sauce mixture into the skillet with the meat and vegetables. Stir well to combine.

Cook over medium heat, stirring constantly, until the sauce has thickened and coated the meat and vegetables, about 2-3 minutes.

In another skillet, heat the remaining 2 tablespoons of vegetable oil over medium-high heat. Add the Chow Mein noodles and stir-fry until they are heated through and slightly crispy.

Serve the Hamburger Chow Mein over the crispy Chow Mein noodles.