The secret here isn't in the seasonings (though the tarragon and sour cream make it pretty wonderful) but in the texture of the chicken, described as "plush" by the chef Barbara Tropp in her "China Moon"...
Smoked chicken is given a husky taste that complements the inherent sweetness of the fowl and brings a hearty note to the pasta it's combined with. The sweeter-smelling the wood used, the more alluring...