Sprinkle chicken with salt and pepper to taste. In a large skillet add olive oil and cook the chicken on medium high heat for 3-5 minutes on each side or until brown on each side and no longer pink in center. Remove chicken and set aside. Add the mushrooms and cook until tender. Set aside.
To make the sauce, add the butter and melt. Add garlic and cook until tender. Whisk in the flour until it thickens. Whisk in chicken broth, heavy cream, parmesan cheese, garlic powder, pepper and salt. Add the spinach and let simmer until the sauce thickens and spinach wilts. Add the chicken and mushrooms back to the sauce and serve over pasta.