In fry pan, saute chicken breasts in one tablespoon olive oil until almost done. Set aside.
In a Dutch oven, heat the remaining one tablespoon of olive oil in a large sauce pot over medium heat. Saute onion, carrots, celery, sweet potato and parsnips for 2 minutes to enhance the natural sugar in them. Add the parsley, dill, basil and tarragon and cook, stirring until fragrant. About 1 minute.
Add the stock and bring to a boil, lower heat to a simmer and cook for 20 minutes until all the vegetables are tender. Add in cooked chicken and cook until chicken is nice and hot. Season with salt and pepper to taste.
Spoon into soup bowls and garnish with chopped fresh parsley.
Notes
Tips For Success:
Don't skip sauteeing the chicken. And don't over-crowd the pan when doing so. A hot skillet will brown the chicken a bit which will add flavor. We call this Maillard Reaction. It's basically the chemical reaction that browns foods which adds flavor. Think about toast, your humble toaster may be king of browning.
I learned years ago that sweet potatoes continue cooking long after the burner is turned off. I now stop cooking them when they're just barely tender so they finish naturally in the hot broth instead of falling apart.
Celery Leaves: When chopping the celery use some of those tender leaves. They're nutritious and add a pop of pure celery flavor. Just rough chop them and throw them in the soup when you add the dry seasonings.