Step 1

In a 5- to 6-qt. Dutch oven combine 4 cups water, the broth, garlic, ginger, and soy sauce. Bring to boiling; reduce heat. Cover and simmer 10 minutes to allow flavors to meld.

Step 2

Add noodles, carrots, and tofu. Simmer, uncovered, 8 minutes, stirring occasionally. Add bok choy, asparagus, mushrooms, and scallions. Simmer, uncovered, 1 minute more. Serve in shallow bowls with lime wedges.