Combine flour, salt, and pepper in shallow dish. Dredge chicken in flour mixture. Heat butter and oil in skillet; add chicken, and saute 3 to 4 minutes on each side. Add Champagne; cook over medium heat about 12 minutes or until chicken is done. Remove chicken, and set aside. Add mushrooms to skillet, and saute 1 to 2 minutes. Add whipping cream to skillet; cook over medium heat,stirring constantly, just until thickened. Add chicken, and cook until thoroughly heated. Serve warm.