Place pasta in same saucepan. Add water; cook over medium-high heat 6 to 8 minutes, stirring frequently, until water is almost completely absorbed and pasta is al dente. Add milk and remaining 1 1/2 teaspoons Cajun seasoning; heat to boiling. Add cheese. Reduce heat to low; cook 1 to 2 minutes, stirring constantly, until cheese is melted and liquid has reduced to a creamy sauce. Stir in sausage, hot sauce, chicken and green onions; cook until heated through. Top with browned bread crumbs; garnish with additional sliced green onions, if desired.