In a bowl, combine regular soy sauce, dark soy sauce, cooking wine, cornstarch, baking soda, and avocado oil.

Add the marinade to the steak. Mix well to ensure an even coat.

Let the steak marinate for 15 minutes. This helps tenderize the meat and boost the flavor.

In a small bowl, mix oyster sauce, dark soy sauce, regular soy sauce, rice vinegar, cornstarch, water, and sugar.

Stir until the cornstarch and sugar are fully dissolved. Set aside.

Preheat a stainless steel pan over high heat until it starts to smoke.

Lower the heat, add a drizzle of avocado oil, and then add the marinated steak slices in a single layer.

Increase the heat back to high and let the steak brown on one side before flipping to brown the other side. Ensure the beef is well-browned but not overcooked.

Remove the beef from the pan and set aside.

In the same pan, add a bit more avocado oil if needed.

Add the chopped white onion and the white parts of the scallion. Stir fry until the onions are just starting to soften but still have a bite to them.

Add the minced garlic and stir fry for an additional 30 seconds, making sure the garlic doesn't burn.

Add the browned beef to the pan with the onions and garlic.

Pour the prepared sauce over the beef and vegetables. Stir well to coat everything evenly.

Continue cooking until the sauce has thickened slightly, ensuring it’s not too thin.

Optionally, add fresh or dried Thai chili for an extra heat.

Turn off the heat and sprinkle with chopped green scallions. The residual heat will cook them.

Finish with a drizzle of sesame oil, a sprinkle of black or white pepper, and a generous pinch of sesame seeds.

Serve hot, garnished with additional fresh Thai chili if desired.