Soba noodles are classically made with 100 percent buckwheat flour, and those are the ones I seek out whenever possible. Those made with a mix of buckwheat and whole wheat are more commonly available and are still plenty tasty.
Put the chicken broth, ginger, garlic, and star anise in a soup pot. Bring just to a boil, lower the heat to maintain a steady simmer, and cook, undisturbed, for 20 minutes. Fish out and discard the ginger and star anise. Stir in the tamari and mirin (if using).
Meanwhile, bring a large pot of water to a boil. Divide the arugula among four large soup bowls.
When the water boils, cook the soba noodles according to the package directions. Drain, quickly rinse with cool running water, and divide the soba among the bowls, dropping them on top of the arugula. Top the soba with tofu and ladle enough broth into each bowl to wilt the arugula and cover the noodles. Garnish with the green onion and herbs, if you like.
Serve immediately with tamari, chile oil, and toasted sesame oil at the table, for people to add as they like.
Molly Watson, Greens + Grains: Recipes for Deliciously Healthful Meals, Chronicle Books (2014). Photo by Joseph De Leo.