Prepare the marinade by combining soy sauce, scallions, garlic, sesame seed, ginger, and sugar in a bowl.

Add sesame oil to the marinade and mix well.

Slice the beef into thin strips.

Marinate the beef in the prepared marinade for at least 15 minutes.

Prepare the vegetables: sliver the carrot, slice the onion, celery, and mushrooms.

Cook the bean thread noodles according to package directions.

Heat a wok or large skillet over medium-high heat.

Stir-fry the marinated beef until cooked through.

Add the prepared vegetables to the wok and stir-fry until tender-crisp.

Add the cooked bean thread noodles to the wok.

Toss everything together to combine and heat through.

Serve immediately.