Cook's Note: If you like a slightly spicy soup use parsnips, for a sweeter soup use fennel.
For the poached chicken breasts:
Place the chicken, leek, onion, celery, carrot, lemon, parsley, dill, thyme, and bay leaf in a large pot and fill with water until the pot is 2 to 3-inches full from the top, about 3 to 4 quarts water. Cover and bring to a boil, then uncover and reduce heat to simmer. Cook uncovered 1 hour. Remove the chicken to large plate or bowl. Strain the cooking liquids and reserve for soup stock. Pull the skin and carcass away and chop the meat or shred with forks.
For the soup:
Heat 2 tablespoons extra-virgin olive oil in soup pot or large Dutch oven over medium-high heat and add leeks, onions, celery, parsnip or fennel, carrots, salt and pepper. Stir frequently for 10 minutes to soften vegetables without browning them then add stock and 1/3 of the chicken meat to pot. Cool and store soup for a make-ahead meal and reheat over medium high flame or, to serve immediately reduce heat to simmer and cook the egg noodles in another pot.
Boil water in a large pot, salt the boiling water and cook the pasta to al dente or with a good-bite left to it. Drain the pasta and toss with butter or a drizzle of oil, stir to combine and coat the noodles evenly.
Cook's Note: Cook the egg noodles separately even if you plan to serve soup right away. Add the noodles hot from cooking them to individual bowls and cover with soup. Cook, cool and store, reheat the noodles in a microwave, covered, or combine with portions of the soup on the stovetop. If you combine the noodles with soup or cook them in soup they will bloat and the leftovers will not be as good as the original soup.
Pour the soup over the noodles in soup bowls and top with fresh dill, parsley, or reserved fennel fronds, if using.