Heat your large heavy-bottomed pot over medium heat, then add olive oil and let it warm until it shimmers.
Season the chicken pieces with salt and pepper, then add them to the pot. Sear until golden on all sides, about 5-7 minutes, creating a fragrant, caramelized crust.
Add chopped onions, carrots, and celery to the pot. Cook, stirring occasionally, until the vegetables soften and release their aromas, about 10 minutes. The vegetables should look slightly translucent and fragrant.
Pour in the chicken broth, then stir in fresh thyme. Bring the mixture to a gentle simmer, watching for bubbling around the edges.
Reduce the heat to low, cover the pot, and let it simmer until the chicken is tender and cooked through, about 20-25 minutes. The broth will deepen in flavor and vegetables will soften further.
Remove the cooked chicken from the pot and shred it into bite-sized pieces using a fork. Return the shredded chicken to the soup, stirring to combine.
Taste the soup and adjust seasoning with salt and pepper as needed. Stir in chopped parsley for a fresh, bright note.
Let the soup rest for a couple of minutes, allowing flavors to meld and the temperature to stabilize.
Ladle the hot, hearty soup into bowls, showcasing the colorful vegetables and tender chicken pieces, ready to serve.
