Cook the rice according to package instructions. Set aside.
In a large stockpot or Dutch oven, melt 1 Tbsp. of butter over medium-low heat. Saute the diced onions, carrots and celery in the butter until softened, about 5-6 minutes.
Add the minced garlic and mushrooms. Cook another 1-2 minutes.
Pour in the broth, poultry seasoning and sat. Add the chicken. Bring to a boil.
Once boiling, reduce the heat to low. Cover and simmer until the chicken is cooked, about 12 minutes. Remove the chicken onto a cutting board and shred with forks.
In a separate saucepan, melt the remaining butter over medium-low heat. Whisk in the flour and cook until bubbling, about 1-2 minutes. Stir in the half-and-half until the mixture is slightly thickened.
Pour the cream mixture, chicken, cooked rice and spinach leaves into the soup mixture. Serve warm.