Why It Works
- The smoky, salty, savory flavor of shoyu-dashi adds an entirely different, and delicious, dimension to salads compared to a classic lemon juice– or vinegar-based dressing.
- Toasting the walnuts in the microwave is quick and easy.
Conventional wisdom says that salads should be dressed with vinaigrettes, which, by definition, balance an acid with a fat. Turns out you can break that rule by dropping the acid entirely. In this salad, we make a "vinaigrette" with shoyu-dashi—soy sauce mixed with dashi—for an easy, deeply flavorful dish.
- 1 pound (500g) sweet potatoes in jackets, poked all over with a fork
- 1 cup walnut halves (3 ounces; 90g), crumbled
- 2 tablespoons (30ml) extra-virgin olive oil, plus more for drizzling
- 2 cups (475ml) cold water
- 1/4 ounce dried kombu (8g; about one 5- by 2-inch piece)
- 1/4 ounce dried bonito flakes (8g; 1 loosely packed cup)
- 2 tablespoons (30ml) soy sauce
- 4 cups arugula (2 1/2 ounces; 70g)
- Kosher salt and freshly ground black pepper
Microwave sweet potatoes until tender and easily pierced with a fork, about 5 minutes. Set aside to cool slightly. If desired, peel and discard jackets. Cut into medium cubes and allow to cool to room temperature.
Meanwhile, on a microwave-safe plate, drizzle walnuts with just enough olive oil to lightly coat, toss well, and arrange in a single even layer. Microwave in 1-minute intervals at high power, tossing walnuts between intervals, until toasted and fragrant, about 3 minutes. Let cool.
In a medium saucepan, combine water with kombu and cook over medium heat until just shy of a simmer. Remove and discard kombu using tongs. Remove from heat, add bonito flakes, and let steep for 10 minutes. Strain dashi into a heatproof container through a fine-mesh strainer. Discard bonito flakes. (See note.)
In a small bowl, whisk 1/4 cup dashi together with soy sauce (this is now shoyu-dashi). Reserve remaining dashi for another use. (It's good just as a warming broth, or can be used to make a quick miso soup.)
In a clean small bowl, whisk together 3 tablespoons shoyu-dashi with 2 tablespoons olive oil. Reserve remaining shoyu-dashi for another use. (It's delicious as a broth for poached eggs, steamed fish, or simple steamed vegetables.)
In a salad bowl, combine sweet potato, walnuts, and arugula. Dress with shoyu-dashi/oil mixture, tossing well to coat. Season with salt and pepper and serve.
Kombu and bonito flakes can be saved and used to make a second, weaker dashi that forms a great base for miso soup.