Spicy Noodle Soup With Mushrooms and Herbs

or olive

thinly sliced

large, thinly sliced

such as maitake, oyster, cremini or shiitake, torn into bite-size pieces

or green, such as Fresno, thinly sliced, or 3/4 teaspoon red-pepper flakes

plus more to taste

unseasoned, plus more to taste

such as udon, soba, rice or spaghetti

tender leaves and stems, such as cilantro, mint, chives, parsley or a mix, for serving

or both, for serving, optional