Cook noodles according to package instructions until just al dente. Drain and set aside.
In a large skillet over medium-high heat, brown the ground beef until fully cooked. Drain excess grease if needed.
Reduce heat to medium and add garlic and ginger. Sauté for 30–60 seconds until fragrant.
In a bowl, whisk together soy sauce, brown sugar, water, cornstarch, black pepper, and red pepper flakes.
Pour sauce into the skillet and stir well. Simmer for 2–3 minutes until thickened.
Add cooked noodles and toss until evenly coated.
Remove from heat and garnish with green onions. Serve immediately.