Udon with Mushroom Broth, Cabbage, and Yams

INGREDIENTS

• 2 teaspoons tamari soy sauce
• 10 ounces Japanese-style udon noodles or soba noodles
• 1 cup sliced green onions
• 2 6-inch strips dried kombu
• 1 1/2 ounces dried shiitake mushrooms, rinsed
• Tamari soy sauce
• 3/4 cup thinly sliced peeled fresh ginger
• 2 cups 1/2-inch cubes peeled yams (red-skinned sweet potatoes)
• 5 ounces snow peas, trimmed
• 4 to 6 ounces semi-firm tofu, cut into 1/2-inch cubes (optional)
• 2 lemongrass stalks, outer dark layers removed, all but bottom 4 inches cut off and discarded
• 1 1/2 cups coarsely chopped fresh cilantro
• 5 ounces slender carrots (preferably assorted colors), peeled, thinly sliced on diagonal
• 3 cups water
• 1/4 cup matchstick-size strips peeled fresh ginger
• Sambal oelek
• 1 teaspoon unseasoned rice vinegar
• 4 cups 1/2-inch-wide crosswise slices cored Napa cabbage