Rinse the chicken and pat with paper towels to dry. Sprinkle with salt and pepper. Melt 4 tablespoons butter in a large sauté pan on medium/high heat. When pan is sizzling, add chicken breasts and sear on each side for 3 to 5 minutes, or until a light brown crust begins to form. Remove chicken and place in a slow cooker.

Using the same pan, add the chopped onions and minced garlic and sauté until onions are transparent in color, about 5 minutes. While sautéing, scrape the bottom of the pan to blend in the burnt bits of seared chicken. Add sautéd veggies to the slow cooker.

Using the same pan, add the bouillon base (or granules or cubes) and water and bring to a quick boil until granules have dissolved. If you're using prepared broth, simply pour 5 cups into the pan. Add in the cream of mushroom soup and whisk until soup and broth are well blended.

Add rice to the slow cooker and place the remaining 4 tablespoons butter on top. Pour soup mixture into the slow cooker over the rice. Cover and cook on HIGH for 3 to 4 hours, or until rice is tender and chicken is cooked through.

Remove lid and shred chicken using two forks. There will be liquid on top of the rice, however; this will get absorbed once everything is combined. Stir the shredded chicken and rice to incorporate all ingredients. Taste for seasonings and add salt and pepper if desired. Sprinkle shredded Parmesan cheese over rice and garnish with parsley.