Put large dutch oven over medium high heat. Add olive oil and brown chicken thighs (seasoned with salt and pepper) in batches, 10 minutes total.
As chicken cooks, dice onion and garlic. Once chicken is browned, remove and set aside, and add in butter and onion to sweat.
Add in garlic to sweat for 1 minute. Slowly add in flour to make roux, stir and cook over medium heat for 2-3 minutes. Add in chicken stock and milk, bring to simmer.
Stir in corn starch, slurried with a splash of water**
Once simmering, add in chicken, mixed vegetables, bay leaves, thyme, and a heavy pinch of salt and pepper. Simmer for at least 15 minutes, or set in slow cooker for up to 6 hours.
As soup simmers, prepare noodles according to the package. Serve soup over noodles with an extra grind of black pepper.
*Yeah, you could dice carrots, shave ears of corn, cut green beans, etc. But the frozen bag, which is generally high quality, saves time and money. Don’t be afraid of this shortcut!
**I use flour and cornstarch here to thicken, which I recognize is unconventional. I prefer how the flour gives the soup body, while the corn starch adds a certain creamy glossiness that I associate with chicken stews.