Miso, or fermented bean curd, is available in many varieties. The mustard-miso dressing here is made with light-colored (white) miso, a milder style. If you prefer a more pungent dressing, use the stronger dark-colored (red) miso.
Bring to a boil in a stockpot:
12 cups water
1 1/2 tablespoons salt
Add and cook for 1 1/2 to 5 minutes, depending on size:
When the asparagus is tender with a slight crunch remaining, drain and rinse under cold water to stop the cooking. Drain well, dry, transfer to a bowl, and set aside. Mix in a small bowl:
1 teaspoon dry mustard
1 teaspoon cold water
Let sit for 10 minutes to develop the flavor of the mustard. Add:
1 tablespoon light-colored miso (white)
Vigorously whisk together to break up the miso until it is smooth. Add:
2 tablespoons minced scallions
1 tablespoon fresh lemon juice
1 tablespoon rice vinegar
2 teaspoons soy sauce or tamari
Pour the dressing over the reserved asparagus and toss well together. Serve chilled or at room temperature.