Melt butter in large nonstick skillet over medium-high heat and cook chicken, in batches if necessary, stirring occasionally, until chicken is thoroughly cooked. Remove chicken and set aside. Stir sauce and broccoli into same skillet. Bring to a boil over medium-high heat. Reduce heat to low and simmer covered, stirring occasionally, until broccoli is heated through, about 5 minutes. Stir in chicken and cook, stirring occasionally, until heated through, about 2 minutes. Serve over hot fettuccine and sprinkle, if desired, with grated Parmesan cheese.