1In a large saucepan or Dutch oven, cook rotini to al-dente, adding broccoli during last 5 minutes of cooking time.
In a medium saucepan, combine sour cream and flour, blend well;stir in milk. Cook over medium heat,stirring constantly, until hot but not boiling. Stir in chicken, basil, mushrooms and 3 Tablespoons of the cheese. Cook until heated through. Drain rotini and broccoli; return to saucepan. Add chicken mixture; toss to coat. Place mixture in a serving dish or platter; sprinkle with remaining cheese.