Heat oil in 4 quart dutch oven or soup pot over medium-high heat.
Add chicken thighs and cook for 2-3 minutes per side, just until lightly browned. Remove from the pot and set aside.
Add the potatoes, carrots, celery and onion and cook for 5-6 minutes until beginning to soften.
Add garlic, salt, parsley, thyme, pepper, and bay leaf. Stir and cook 1 minute.
Add 2.5 cups of chicken broth to the pot and scrape the bottom well to remove any browned bits. Bring to a simmer over medium-high heat.
Add the chicken thighs back to the pot, pressing them down into the liquid.
Cover and reduce heat to low. Simmer for 15-20 minutes, until potatoes and carrots are tender.
Remove chicken and shred.
Whisk together remaining half cup broth and corn starch and add back into the pot with the chicken.
Cook for 2-3 minutes until slightly thickened. Serve with fresh parsley if desired.
