Put the broth in a large soup pot, add the vegetables (onion, celery, carrot, and garlic if using) and bring to a boil. Reduce heat and simmer 10 minutes, until vegetables are tender-crisp.**
Add the noodles and cooked chicken to the soup, bring back to a boil, and simmer 8 minutes or until the noodles are just barely tender.
Season with salt and pepper and serve immediately.
Notes
*To start with uncooked chicken:
Either sauté boneless chicken breasts or thighs in a pan or add them to the broth before the vegetables and cook thoroughly, 15-20 minutes for whole breasts, 10 minutes for diced chicken.
When the chicken is cooked, allow to cool and then cut into pieces, if needed while vegetables are cooking.
Set it aside to add with the noodles. I've found adding it later helps retain the chicken flavor by not letting it boil out in the soup while the vegetables are cooking.
Make Ahead: Chicken noodle soup freezes well - cook the noodles to just al dente, cool and transfer to freezer-safe containers. Alternately, you can freeze without the noodles and add when reheating (or just leave out for a lower carb option).**Lower Carb Chicken Vegetable Soup Variation: omit the noodles and add other vegetables like parsnips, cabbage, kale, and/or spinach. With this option, you'll skip step 2, adding all the vegetables and meat in step 1 and cooking for 15 minutes until all vegetables are tender, making it even quicker to make.