Cook rice according to the directions on the package.
Halfway through the rice cooking, melt 1 tablespoon of butter in a large soup pot over medium-high heat. Once melted and bubbling, add the sliced mushrooms and cook 6-7 minutes, until tender and golden. And all moisture has cooked off. Remove to a plate.
Add 2 tablespoons of butter to the pot and add the chopped onions, carrots, and celery. Sauté 5-6 minutes, or until slightly tender, stirring often. Add the minced garlic and sauté for 30 seconds.
Pour in the chicken broth and add the seasonings: sage, rosemary, and thyme. Season with salt and pepper, to taste. Using a wooden spoon, stir to combine making sure to scrape any of the bits on the pan from sauteeing.
Raise the temperature to medium-high, add the chicken breast to the pot and bring it to a boil. Cover the pot with a lid and allow the soup to boil for 10-12 minutes, or until the chicken has cooked through. If the chicken breast is on the thicker side, cooking time may increase. I suggest not only flipping each breast halfway through, but also checking the internal temperature with a digital meat thermometer to ensure the thickest part of the breast reaches 165 degrees F.
Reduce the heat to a simmer. Remove the chicken to a plate or cutting board to cool for a few moments. Shred into bite-size pieces using two forks.
While the chicken is cooling, place a medium saucepan over medium heat. Add the remaining 4 tablespoons of butter and 1/2 cup of flour. Cook for 1 1/2 – 2 minutes, whisking the entire time to combine.
While whisking, slowly pour in the milk to combine with the butter and flour mixture. Cook until the mixture has thickened.
Add the milk mixture to the pot and cook for 5-7 minutes, stirring until the soup has thickened. Taste test the broth and add additional seasonings, if needed for your taste preferences.
Add the cooked rice and mushrooms, as well as the chopped kale, to the pot and stir to combine.
Pour in the half and half, stirring to fully combine. Allow the kale to cook until it has just started to wilt.
Serve garnished with freshly shredded parmesan cheese, freshly chopped parsley, and your favorite garlic bread or cheesy toast!