Marinate chicken thighs in fish sauce and pepper for 15 minutes. While the chicken is marinating, cut your onions, garlic, carrots, potatoes, and mushrooms.
Heat 1 tbsp of oil in a dutch oven or large soup pot. Sear the chicken on all sizes. Make sure to save the fish sauce marinade for later. Set aside.
Add the onion to the pot, and cook for 2-3 minutes until the onion becomes slightly brown. Add the garlic and salt and cook for 30 seconds.
Next, add the ground cinnamon, tomato paste, and fish sauce marinade to the pot. Mix.
Add the seared chicken back to the pot and mix until the chicken is coated in the sauce. Cover and lower the heat to medium low and let the chicken cook for 10 minutes.
Pour the chicken broth into the pot and add the bay leaves, carrots, and potatoes. The broth should cover 80% of the ingredients. If you feel like there is not enough liquid, add water or more broth. Cover and cook for 10-15 minutes until both are cooked through.
Lastly, add the mushrooms to the pot and cook for 5-10 minutes until cooked through.
Taste the broth to make sure it is seasoned to your liking. If it tastes too bland, add more salt until it is perfect for your tastes. Serve with a baguette or rice.