Japanese soups have some of the most unique and complex flavors and aromas. When I first tried udon soup made with dashi broth many years ago, I was not a fan at all. But over the years I've come to really enjoy the unique layers of flavor, or what the Japanese call umami, the fifth taste, in the traditional broth. Udon, one of the most popular noodles in Japanese cuisine, originated from China and were brought to Japan by returning Buddhist monks. In restaurants you will find this soup accompanied by different toppings, such as kamaboko (fish cakes), abura-age (deep-fried tofu pockets), cooked meat, tempura shrimp, or an egg poached in the broth.
This is what I like best about Asian soups, that the choices for toppings/ingredients are completely personal. If you're having a dinner party and serving this soup, the clear broth and noodles can be ladled into bowls and every guest can choose from a selection of toppings: thinly sliced vegetables such as carrots, snow peas, mushrooms, and scallions; various greens such as spinach, chard, and watercress; and proteins. My personal favorite combination is what I've come up with for this recipe. It includes tofu, watercress, shitakes, carrots, and scallions. These fresh vegetables are full of vitamins and minerals, making this soup a very healthy meal.
To start the recipe, I first make the dashi, a fundamental stock in Japanese cooking, which combines kombu (kelp) with katsuobushi (dried tuna flakes), steeped in hot water. The broth is additionally flavored with the soaking liquid from dried shitakes, soy sauce, mirin, and sugar. Meat or tofu can be added next as well as the noodles. For something extra special, the soup can be topped with the aforementioned kamaboko, abura-age, or tempura shrimp. Lastly for those who prefer the soup a bit spicy, the Japanese seven-spice mix, shimichi tōgarashi, which combines hot pepper, Szechuan pepper, sesame seed, poppy seed, hemp seed, orange peel, and nori (roasted seaweed), can be sprinkled into the broth. I just love adding it to a hearty and healthy bowlful.
Udon Noodle Soup with Tofu and Watercress
4-1/2 cups water
1/4 cup loosely packed katsuobushi (bonito flakes)
3-inch piece kombu
1-1/2 cups mushroom broth from dried shitakes or vegetable stock
2 tablespoons soy sauce
2 tablespoons mirin
2 tablespoons sugar
fine sea salt
6 ounces dried udon noodles
1 8-ounce package firm tofu, drained and cut into 1/4-inch cubes
1 bunch watercress, thick stems removed
6 ounces shitake mushrooms, stems removed, sliced
1 carrot, julienned
2 scallions, sliced on the bias
Bring water to a boil in a saucepan. Lower to a simmer and add katsuobushi and kombu. Cover and let steep for 15 minutes off from heat. Strain dashi broth into sieve lined with cheesecloth placed over a bowl.
Return dashi to saucepan and bring back to a simmer. Add mushroom broth, soy sauce, mirin, and sugar. Season with salt.
Meanwhile bring a pot of liberally salted water to a boil. Add udon and cook until al dente, about 5 to 7 minutes. Drain and rinse udon under cold water.
To the dashi add tofu, udon, watercress, shitakes, and carrot sticks. Let the tofu and udon warm through and the watercress wilt. Divide into bowls. Season with shichimi tōgarashi if desired. Yield: 4 servings.