Sauté the Veggies: Place a large Dutch oven or heavy soup pot over medium heat. Melt the unsalted butter. Add the diced onion, carrots, and celery. Sauté for 5-7 minutes until the onions are translucent and the vegetables begin to soften and release their natural sweetness.
Bloom the Spices: Stir in the minced garlic, dried thyme, and black pepper. Cook for just 1 minute, stirring constantly, until the garlic is fragrant. (Do not let the garlic burn!).
Cook the Chicken: Add the cubed chicken breast to the pot. Cook for 4-5 minutes, stirring occasionally, until the outside of the chicken is no longer pink.
Simmer the Broth: Pour in the salt-free chicken broth and add the bay leaves. Bring the soup to a gentle boil, then immediately reduce the heat to low. Cover the pot and let it simmer gently for 15-20 minutes to ensure the chicken is cooked through and the flavors meld together.
Cook the Noodles (Separately): While the soup simmers, bring a separate medium pot of plain water to a boil. Cook the egg noodles according to the package directions until al dente. Drain the noodles and set them aside. (Cooking them separately prevents them from soaking up all your broth and turning mushy!).
The Final Touch: Remove the soup pot from the heat. Carefully fish out and discard the bay leaves. Stir in the fresh chopped parsley and the fresh lemon juice. Taste the broth—if it needs a little more "zing," add another squeeze of lemon or a pinch more black pepper.
Serve: Place a portion of the cooked noodles into each serving bowl, then ladle the hot, savory chicken and vegetable broth over the top. Enjoy immediately!