1. Mix chicken, cheese, sour cream and chilies in 2-quart casserole. Cover tightly and microwave on medium (50%) 8 to 10 minutes, stirring every 3 minutes, until cheese is melted and mixture is hot.
2. Place about 2 cups of the tortilla chips on each of 4 serving plates; spoon chicken mixture over chips. Top with tomatoes and avocado. Serve with salsa if desired.