Korean-Style Steak and Noodles with Kimchi

Name: Korean-Style Steak and Noodles with Kimchi
Prep time: 20 min
Total time: 20 min
Cuisine: Asian, Korean
Ingredients: 0.25 cup reduced-sodium soy sauce; 2 tablespoon rice vinegar; 2 tablespoon packed brown sugar; 1 tablespoon toasted sesame oil; 1 tablespoon gochujang or 1 tsp. sriracha sauce; 1 pound flank steak or skirt steak; 8 ounce rice noodles, soba noodles, or cellophane noodles; 2 tablespoon vegetable oil; 8 ounce shiitake mushrooms, stemmed and sliced; 1 cup packaged julienned carrots or coarsely shredded carrots; 6 green onions, cut into 1-inch pieces (white and green parts); 2 cup fresh baby spinach; 1 cup kimchi, coarsely chopped; Toasted sesame seeds (optional); Sriracha sauce (optional)