In a bowl, add beef (separate into smaller pieces if needed), cornstarch, white pepper, and garlic powder. Mix until evenly combined.
Heat a large frying pan over medium-high heat and add olive oil.
Add the coated beef and fry for 2 - 3 minutes until golden brown and just cooked. Cook in batches if needed as to not over crowd pan.
Remove the beef from the pan, add a drizzle of olive oil, add the veggies, and a sprinkle of salt and black pepper.
Sauté until veggies are softened, about 6-7 minutes.
In the meantime, heat up udon noodles per package directions, drain, toss with a tsp of oil to avoid sticking, and set aside.
In a small bowl, mix together sauce ingredients.
Once veggies are done, add back in beef, noodles, and sauce. Toss until evenly combined.