In a bowl, whisk together the oyster sauce, soy sauce, dark soy sauce, granulated sugar, pepper, and Sriracha until fully combined. Set aside.

In a separate bowl, combine thinly sliced beef with baking soda, garlic powder, and half of the prepared sauce. Mix well and let marinate for 15-20 minutes.

Heat cooking oil in a wok over medium-high heat. Add marinated beef and stir-fry for 1-2 minutes until slightly pink. Set aside.

In the same wok, add more oil if needed, then add sliced onion and Chinese broccoli. Stir-fry for 1-2 minutes until tender-crisp.

Add rice noodles and half of the remaining sauce. Toss gently for 1-2 minutes to coat the noodles.

Stir in bean sprouts and dark green parts of green onions with remaining sauce. Toss again for another 1-2 minutes.

Return the cooked beef to the wok and gently combine with the noodles and vegetables. Adjust seasoning with salt if needed. Plate and garnish with white parts of green onion.