2 1/2 Tbsp ginger, peeled and grated
2 Tbsp low-sodium soy sauce
1/4 tsp crushed red pepper
3 garlic cloves, minced
8 ounces flank steak, cut into 1 1/2-inch wide strips and thinly sliced
1 Tbsp peanut or canola oil
6 cups thinly sliced bok choy (about 1 pound)
1 cup (about 2 ounces) shiitake mushrooms, thinly sliced
1 cup carrot, sliced
1/2 cup green onions, thinly sliced
2 cups hot water
2 Tbsp hoisin sauce
2 Tbsp low-sodium soy sauce
2 (14-ounce) cans less-sodium beef broth
4 ounces uncooked soba (buckwheat) noodles
1 Tbsp rice vinegar
1 1/2 tsp dark sesame oil, divided
Combine the first 5 ingredients in a large zip-top plastic bag, and seal. Marinate in refrigerator 2 1/2 hours, turning bag occasionally.
Heat oil in a small Dutch oven over high heat until it begins to smoke. Add beef mixture to pan; stir-fry 1 minute or until browned. Remove beef mixture from pan; set aside.
Add bok choy, mushrooms, carrot, and green onions to pan; stir-fry 2 minutes or until bok choy begins to wilt. Add water, hoisin, soy sauce, and broth; bring to a boil. Stir in noodles. Reduce heat; simmer 5 minutes or until noodles are done. Stir in beef mixture and vinegar. Ladle 1 1/2 cups soup into each of 6 bowls; drizzle each serving with 1/4 tsp sesame oil.