Marinate the beef

• Add the sliced sirloin to a bowl with the baking soda, soy sauce, oyster sauce and black pepper.
• Mix well and let marinate.

Mix the udon sauce

• In a separate bowl, whisk together the soy sauce, dark soy sauce, brown sugar, oyster sauce, sake, sesame oil and black pepper.
• Set aside.

Sear the beef

• Heat a little oil in a hot wok or large skillet.
• Add the marinated beef and cook until nicely browned.
• Remove from the pan and set aside.

Stir-fry the vegetables

• In the same pan, add the yellow onion, garlic, shredded carrots, bok choy and green onions.
• Stir-fry until the vegetables begin to soften but still have a little crunch.

Add noodles, beef and sauce

• Add the udon noodles, followed by the cooked beef and the prepared sauce.

Toss and serve

• Toss everything together until the noodles and beef are evenly coated in the sauce and everything is heated through.
• Serve hot.