Bake chicken thighs on 375 for 8 min and then flip and cook for another 12 min (chicken should be close to fully cooked but can be a little pink inside as it will go back in the soup later). Remove and shred.
Using tongs, toast the chilies over a flame until they become pliable and blistered. I used my gas burner which worked great. Remove and split open and remove the seeds. Roughly chop and add to a large pot or dutch oven.
Add in the fire roasted tomatoes. Using an immersion blender, blend together the chilis and tomatoes (alternatively you could use a blender). Remove from pot and set aside.
In same pot, add olive oil, onion, salt and pepper and let cook for about 8 minutes. Add in garlic and cook for another 2min. Add in the chili tomato mixture and blend together (again, either remove and use a blender or keep in pot and use an immersion blender). Once blended, turn pan to high heat and let the mixture thicken to almost a paste. Add chicken broth and bring to a boil. Reduce heat to low and let sauce simmer for about 20 min. Taste test broth and add more salt if needed.
At this point you can add in your bok choy and keep cooking for another 5 min or so or until greens are wilty. Add in your shredded chicken and cook for another 5 min to blend everything together and ensure chicken is fully cooked through. Remove from heat and add juice of a lime and mix. Serve with whatever toppings you prefer. Enjoy!
