Spicy Korean Beef Noodles

Name: Spicy Korean Beef Noodles
Prep time: 5 min
Cook time: 25 min
Total time: 30 min
Cuisine: Asian
Ingredients: 1 lb flank steak; 2 tablespoons oil; 4 tablespoons gochujang (Korean chile paste found in the Asian section of most grocery stores- see note); 2 tablespoons thinly sliced green onions; 2 tablespoons soy sauce; 2 tablespoons rice vinegar; 4 teaspoons minced garlic; 1 teaspoon ground ginger; 1 tablespoon sesame oil; 4 teaspoons sugar; 2 (3 ounce) packages beef ramen noodles, including seasoning; 2 cups water; 1/2 white onion, thinly sliced; 1/2 cup sliced mushrooms