Season chicken with a bit of the Italian seasonings and salt and pepper on both sides. Cook in a large nonstick skillet on the stove over medium-high heat 1-2 minutes on each side until browned on the outsides.
Transfer chicken to a greased slow cooker. Add chicken broth, butter, mushrooms, onions, garlic, remaining Italian seasoning, and salt and pepper to slow cooker.
Cover and cook on high for 1-2 hours or on low for 3-4 hours. Stir in orzo, cover and cook for another 30-45 minutes on high.
Uncover and use a fork to pull chicken out of the slow cooker. Stir contents of slow cooker, then return chicken to slow cooker, on top of the orzo mixture.
Sprinkle parmesan cheese over chicken. Cover and cook until cheese is melted, about 5-10 minutes. Serve with fresh herbs and cracked black pepper if desired.
