First, cook the ramen noodles according to the package instructions. Drain and set aside.

Next, in a large skillet, heat the vegetable oil over medium-high heat. Add the sliced beef and cook until browned, about 3-4 minutes.

Then, add the sliced onion to the skillet and cook until it becomes translucent, about 5 minutes.

Also, stir in the minced garlic and ginger, cooking for another 1-2 minutes until fragrant.

Now, sprinkle the Korean chili flakes over the beef mixture and stir to combine.

So, in a small bowl, whisk together the soy sauce, sesame oil, brown sugar, and rice vinegar. Pour this mixture over the beef and onions.

Stir well to combine and cook for another 2-3 minutes until the sauce thickens slightly.

Finally, add the cooked ramen noodles to the skillet and toss everything together until the noodles are well coated with the sauce. Cook for another 2-3 minutes.

Serve the Korean Beef Noodles hot, garnished with chopped green onions and sesame seeds.