Arugula Sweet Potato and Walnut Salad With Dashi Vinaigrette Recipe

Name: Arugula, Sweet Potato, and Walnut Salad With Dashi Vinaigrette Recipe
Ingredients: 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