- 1 1/2 ounces dried porcini mushrooms
- 6 garlic cloves, gently smashed
- 1 small bunch thyme
- 2 bay leaves
- 1/2 teaspoon whole black peppercorns
- 1 1/2 cups medium egg noodles
- Kosher salt
- 12 ounces wild mushrooms, cut into 1/4″ pieces if large
- 2 medium carrots, peeled, cut into 1/8″-thick slices
- 2 stalks celery, cut into 1/8″-thick slices
- 3 scallions, thinly sliced, green and white parts separated
- Freshly ground black pepper
- 2 tablespoons celery leaves, coarsely chopped
- Submerge porcini mushrooms in 3 quarts cold water in a large bowl. Let stand at room temperature at least 2 hours or chill overnight.
- Pour mushrooms and liquid into a fine-mesh sieve set over a wide heavy pot, gently pressing mushrooms to extract as much liquid as possible. Reserve mushrooms for another use.
- Add garlic, thyme, bay leaves, and peppercorns to pot and bring to a simmer over medium-high heat. Reduce heat to medium-low and gently simmer, stirring occasionally, until broth is reduced to 6 cups, about 1 hour. Strain broth through fine-mesh sieve into a large bowl; discard solids. Return broth to pot.
- Cook noodles in a large pot of boiling salted water, stirring occasionally, until just al dente, 7–8 minutes. Drain; rinse under cold water.
- Meanwhile, bring Mushroom Broth to a simmer over medium-high heat. Add wild mushrooms, carrots, celery stalks, scallion whites, 1 tsp. salt, and 1/8 tsp. pepper; simmer until tender, about 5 minutes.
- Add noodles and scallion greens to soup; season with salt and pepper. Transfer to a large serving bowl and top with celery leaves.
- Soup (without noodles) can be made 3 days ahead. Let cool, transfer to an airtight container, and chill.