Marinate Beef: In a mixing bowl, combine the sliced beef with salt, soy sauce, cornstarch, and baking soda. Let marinate for 20-30 minutes at room temperature.

Prepare Noodles: Cook udon noodles according to the package instructions, aiming for 1-2 minutes less than suggested. Drain and toss lightly with vegetable oil.

Stir Fry Beef: Heat the wok over high heat, add vegetable oil, and stir-fry marinated beef for 3-4 minutes until browned. Cook through, then transfer to a plate.

Sauté Aromatics: In the same wok, add more oil if needed, then stir-fry garlic, ginger, and the white onion for 30 seconds. Add chilies, bell pepper, and carrot, cooking for 2-3 minutes.

Combine Ingredients: Pour in oyster sauce, dark soy sauce, brown sugar, and chicken stock, bringing to a simmer. Add the noodles and beef back, tossing everything together for 2-3 minutes.

Serve: Garnish with green onions and sesame seeds, serve hot, and enjoy!