In a small bowl, whisk together soy sauce, oyster sauce, brown sugar, ginger, garlic, sesame oil, red pepper flake & ground black pepper; set aside.
Stir Fry
In a large pot of boiling water, cook udon noodles according to package instructions; drain well.
Heat olive oil in a large skillet over medium high heat. Add beef & onions. Cook, flipping once, until browned, about 3-4 minutes; set aside.
Stir in mushrooms, broccoli & carrots to the skillet. Cook, stirring frequently, until tender, about 3-4 minutes. Stir in udon noodles, beef & soy sauce mixture until well combined, about 2-3 minutes.
Serve immediately.
Recipe Notes
Udon noodles are a type of thick, chewy Japanese noodle made from wheat flour, water, and salt.