Season the chicken breasts with salt and pepper, then heat olive oil in a large pot over medium heat. Sear the chicken until golden brown on both sides, about 4-5 minutes per side. Remove and set aside to let it rest.
In the same pot, add chopped onion, celery, and carrot. Sauté until the vegetables are tender and aromatic, about 5 minutes, stirring frequently. Add the minced garlic and cook for another minute until fragrant.
Pour in the chicken broth and bring to a gentle simmer. Meanwhile, slice the rested chicken into bite-sized pieces or shred with two forks. Add the chicken to the simmering broth along with fresh thyme, if using.
Once the broth is simmering, add the egg noodles and cook according to package instructions, usually 8-10 minutes, until al dente. During this time, occasionally skim off any foam or impurities that rise to the surface for clarity.
Taste the broth and adjust seasoning with salt and freshly ground pepper. Zest the lemon directly over the soup to add brightness, then squeeze in a little lemon juice if desired for extra zing.
Garnish the soup with chopped parsley or dill for a fresh, herbal finish. Ladle into bowls, ensuring a good mixture of noodles, chicken, and vegetables in each serving. Serve hot and enjoy its comforting aroma and hearty textures.
