Cook pasta, drain and keep warm. Place the chicken and 2 tablespoons dry salad dressing mix in a bag and shake to coat. Melt butter in skillet and add chicken and garlic. Cook over med hi heat stirring until chicken is no longer pink about 5-6 minutes, reduce heat to medium stir in onions and red peppers, cook, stirring occasionally, until all is heated thru about 2-3 minutes.
In a medium bowl stir together sour cream, light cream, and remaining salad dressing mix then stir in hot, cooked pasta. Spoon pasta onto serving platter, top with hot chicken mixture and parmesan if desired.