Cook the Udon Noodles: Bring a large pot of water to a boil. Add the udon noodles and cook according to package instructions (usually around 5-7 minutes). Once cooked, drain the noodles and set aside.
Marinate the Beef: In a bowl, combine the sliced beef with soy sauce, oyster sauce, and half of the black pepper. Let it marinate for at least 10 minutes to absorb the flavors.
Sauté the Vegetables: Heat vegetable oil in a large skillet or wok over medium-high heat. Add the sliced onions and bell peppers, and stir-fry for about 2-3 minutes until they become slightly tender. Add the minced garlic and ginger, cooking for an additional minute until fragrant.
Cook the Beef: Push the vegetables to the side of the skillet and add the marinated beef to the center. Stir-fry for about 3-4 minutes or until the beef is browned and cooked through.
Combine Noodles and Seasoning: Add the cooked udon noodles to the skillet and drizzle with sesame oil. Sprinkle the remaining black pepper over the noodles. Toss everything together until well combined and heated through, ensuring the noodles are evenly coated with the sauce and seasonings.
Serve: Dish out the beef black pepper udon into bowls and garnish with chopped spring onions and sesame seeds.
Notes
Adjust the amount of black pepper according to your spice preference.