Combine all of the seasonings in a small bowl. Season the chicken breast on all sides with half of the seasoning.
Place a pot on the stove at medium-high heat. Add 1 tablespoon of olive oil. Place the chicken breast in the pot. Sear on both sides for 2 minutes or until golden brown. Remove the chicken breast and set aside.
Lower the heat to medium. Add 1 tablespoon olive oil. Stir in the carrots, celery, and onion. Saute for 5 minutes. Season with the rest of the seasoning. Stir in the mushrooms and saute for another 5 minutes.
Add the chicken broth and bay leaves to the soup and bring to a boil. Place the whole chicken breasts into the pot and simmer for 20 minutes.
Remove the chicken from the pot and let it rest for 5 minutes. Use two forks to shred the chicken. Return the shredded chicken to the pot. Add in the tortellini and simmer for 10 minutes. Serve hot.
Notes
When searing the chicken, wait for the pot to reach a high heat. You want the sear to make the outside of the chicken golden brown in less than 2-3 minutes. This will keep the chicken from drying out when you simmer it in the pot.
I like to let the chicken cool for about 5 minutes after it simmers in the pot and before I shred it. I use a fork to shred the chicken because I prefer the large chunks. If you want smaller pieces of chicken, you can place the chicken in a standing mixer and mix with a paddle attachment and it will shred it for you.
Season throughout the cooking process to layer in the flavor. Taste the soup at every step so that you can taste the flavor developing.