In a large pot, heat the olive oil over medium heat. Add the onion and a pinch of salt. Cook, stirring occasionally, until the onion is translucent and soft, about 4–5 minutes.
Add the garlic and cook for about 30 seconds, until fragrant but not browned.
Submerge the chicken breasts in the pot. Pour in the chicken broth. Bring to a gentle simmer, then reduce heat to maintain a light simmer.
Skim off any foam that rises to the surface. This keeps the broth clear and the flavors clean.
Let the chicken cook slowly for about 12–15 minutes, until it reaches an internal temperature of 165°F (74°C) and is cooked through.
Carefully remove the chicken to a cutting board. Add the carrots and celery to the broth and simmer for 8–10 minutes until tender.
Meanwhile, shred or dice the cooled chicken into bite-sized pieces. Return the chicken to the pot.
Stir in the egg noodles, thyme, and parsley. Cook for 6–8 minutes, or until the noodles are tender to your liking.
Season with salt and pepper to taste. If you like a brighter finish, stir in lemon juice just before serving.
Taste and adjust. If the soup tastes too plain, a small splash of soy sauce or a pinch of paprika can add a subtle depth without overpowering the dish.