Pour 32 ounces low-sodium chicken stock into a large pot and bring to a boil over high heat. Reduce heat to a simmer.
Add 2 carrots (peeled and chopped, about 1 cup), 1 stalk celery (chopped, about 1/2 cup), 1 leek (white and light green part thinly sliced, about 1 cup), 2 large chicken breasts or thighs (bone in), and 2 teaspoons Vegit (or other salt-free herb seasoning). Stir once to combine.
Simmer, partially covered, until the chicken is cooked through and the vegetables are tender, about 20–25 minutes. (Check doneness by an instant-read thermometer — chicken should reach 165°F / 74°C — or cut into the thickest part to ensure no pink remains.)
Use tongs to remove the chicken to a plate or cutting board. Let it cool until you can handle it, then remove and discard the bones and skin. Tear or chop the meat into bite-size pieces.
Return the shredded/chopped chicken to the pot. Add 1 cup cooked egg noodles or pasta and stir. Heat just until the noodles and chicken are warmed through, about 2–3 minutes.
Ladle into bowls and serve hot.