Place the chicken thighs in a large heavy-bottomed pot and cover with cold water, ensuring they're submerged.
Bring the water to a gentle simmer over medium heat, skimming off any foam that rises to the surface with a spoon.
While the broth simmers, chop the onion, carrots, and celery into small, uniform pieces.
In a separate pan, heat olive oil over medium heat, then add the chopped vegetables. Cook for about 5-7 minutes until they soften and release a sweet, fragrant aroma.
Add the sautéed vegetables into the simmering broth along with sprigs of thyme for added flavor.
Continue simmering the broth uncovered for 1.5 to 2 hours, until the chicken is tender and falling apart.
Remove the chicken from the pot, shred the meat with two forks, and set aside.
Strain the broth through a fine sieve or strainer into a clean pot to remove solids, leaving a clear, flavorful liquid.
Return the strained broth to the stove, add the shredded chicken back in, and season with salt and pepper to taste. Add a splash of lemon juice or vinegar to brighten the flavors.
Finish by sprinkling chopped parsley over the soup for a fresh, vibrant touch.
Serve hot, ladled into bowls with your favorite accompaniments, and enjoy the comforting, aromatic chicken soup.