Double-Dark Chicken Noodle Soup

Trim dark green leaves from leek; discard all but 2. Slice leek in half lengthwise; set aside. Tuck parsley, thyme, and bay leaves inside leek leaves; tie closed with kitchen twine.
Heat oil in a large heavy pot over medium. Working in batches, cook wings, turning often, until browned all over, 15-20 minutes. Transfer to a plate.
Add onion, carrots, celery, garlic, and reserved leek to pot. Cook, turning occasionally, until browned, 10-12 minutes. Add tomato paste; cook, stirring, until slightly darkened, about 3 minutes. Add 1/2 cup water, scraping up browned bits. Add wings, leek bundle, peppercorns, and 12 cups water; bring to a boil. Reduce heat; simmer, skimming occasionally, until stock is deep amber and chicken is falling off the bone, 1 1/2-2 hours. Remove chicken and vegetables. Strain stock into a clean large heavy pot.
Bring stock to a simmer over medium-high heat; season with salt and pepper. Add thighs, cover, and simmer until cooked through, 8-10 minutes. Transfer thighs to a plate; let cool slightly. Shred meat; discard bones.
Add carrots and onions to pot; simmer until tender, about 5 minutes. Add meat. Meanwhile, cook noodles in a pot of boiling salted water until just al dente, 7-8 minutes. Drain; rinse under cold water. Add to soup. Serve topped with chervil.
Do ahead: Soup (without noodles) can be made 2 days ahead (or 2 months if frozen). Let cool; transfer to airtight containers and chill.