Place the whole chicken in a large pot with water, onion, 2 carrots, 2 celery stalks, garlic, bay leaves, and peppercorns, then bring to a boil. When you see a rolling boil, keep it there just long enough for liquid to fully heat through.

Skim foam, reduce heat, and simmer for 1 hour until the chicken is very tender. Look for gentle bubbles and a broth surface that clears after skimming.

Remove the chicken and strain and reserve the broth, then shred all chicken meat. Let the shredded chicken cool slightly so the texture stays fluffy, not stringy.

Return the broth to the pot, add the butter, and bring it to a simmer. Wait for small bubbles around the edges before continuing.

Add the remaining sliced carrots and celery and cook for 10 minutes until tender. Watch for bright color and fork-tender pieces.

Add the egg noodles and cook for 6-8 minutes. Stir occasionally and cook until noodles are tender but still have a firm bite.

Return the shredded chicken, stir in fresh parsley, and season very generously with salt and pepper. Taste at the end and adjust until the flavor is bold and balanced.