Add the ground beef to a large skillet over medium-high heat. Cook until browned, breaking it apart as it cooks. Season with salt and black pepper to taste. Drain any excess grease if needed.

Add the mushrooms and broccoli into the skillet.

Add 1/3 of water to the skillet and cover to let the broccoli steam for a few minutes.

While the broccoli is steaming, cook the ramen noodles according to the package directions, leaving out the seasoning packets. Drain and set aside.

In a bowl, whisk together the soy sauce, chicken broth, brown sugar, hoisin sauce, garlic, ginger, sesame oil, and red pepper flakes.

Pour the Mongolian sauce over the beef, mushrooms, and broccoli. Stir until everything is well combined.

Whisk together the cornstarch and cold water. Pour the slurry into the skillet and let everything simmer for a few minutes until the sauce thickens.

Add the cooked ramen noodles and toss until everything is coated in the sauce.