Set a large soup pot or Dutch oven on the stovetop over medium heat. Add the oil, onion, carrots, and celery. Cook for 5 minutes, stirring often, until the vegetables begin to soften.

Stir in the garlic and cook for 30 seconds, just until fragrant.

Add the chicken thighs, chicken broth, dried parsley, dried thyme, salt, pepper, and bay leaf. Increase the heat to medium-high and bring the broth to a gentle boil.

Reduce the heat to medium-low, cover the pot partly, and simmer on the stovetop for 15 to 18 minutes, until the chicken is tender and easy to shred.

Transfer the chicken to a cutting board. Keep the soup at a steady simmer over medium-low heat. Shred the chicken with two forks.

Add the egg noodles to the simmering broth and cook for 6 to 8 minutes, stirring occasionally, until the noodles are tender.

Return the shredded chicken to the pot and stir in the frozen peas. Simmer for 2 to 3 minutes, until the peas are warmed through.

Remove the bay leaf. Stir in the lemon juice and fresh parsley, if using. Taste and adjust with more salt or pepper before serving.