Melt 8 T of butter in a bowl; combine with Magic Cajun seasoning and chicken. Heat large skillet over high heat until hot, about 4 minutes. Add chicken pieces and brown about 2 minutes on one side and about 1 minute on the other. Add mushrooms; cook 2 minutes. Add onions, parsley, garlic and stock; cook 2 minutes longer or until sauce is boiling rapidly. Add remaining butter cut into pats, stirring and shaking pan to incorporate. Cook 3 minutes, then add cooked pasta and spinach. Stir and shake pan to mix well.