3 tablespoons soy sauce

1 tablespoon rice vinegar

2 teaspoons sesame oil

8 ounces soba noodles

4 tablespoons grapeseed or other neutral oil

2 cups loosely packed julienned carrots

1 1/2 cups thinly sliced white or yellow onions

1 pound asparagus, end trimmed, sliced on the bias 1/4-inch thick (about 3 cups)

3 cups 1/4-inch-thick slices shiitake mushrooms (from about 7 ounces)

1/2 to 1 teaspoons kosher salt, plus more to taste

2 cloves garlic, minced

pinches red pepper flakes or hot sauce, optional

1/3 cup shelled edamame, optional