Both fragrant and flavorful, Vietnamese noodle soup (pho), will fill your kitchen with sensational smells and your belly with a savory meal.
Combine 2 tablespoons rice vinegar and honey in small bowl. Place beef Flank Steak and vinegar mixture in food-safe plastic bag; turn steak to coat. Close bag securely and marinate in refrigerator 6 hours or as long as overnight, turning occasionally.
Combine water, broth, onion, fish sauce, remaining 2 tablespoons vinegar, garlic, ginger and star anise in stockpot; bring to a boil. Reduce heat; simmer 30 minutes. Meanwhile, remove steak from marinade; discard marinade. Place steak on grid over medium, ash-covered coals. Grill, covered, 11 to 16 minutes (over medium heat on preheated gas grill, covered, 16 to 21 minutes) for medium rare (145°F) to medium doneness (160°F), turning once. Remove steak; keep warm.
Strain broth mixture and discard solids; return broth mixture to stockpot. Keep warm over low heat. Prepare noodles according to package directions using soaking or stir-fry method. Add noodles and any beef juices from steak to broth.
Divide soup among 6 large bowls; serve with sprouts, basil, cilantro and onions, as desired. Carve steak across the grain into thin slices and add to soup. Serve soup with chili sauce, Sriracha , hoisin and lime, if desired.