I've made this several times in the past few years, and it always surprises me how good it is. Very simple to make; I omit the sugar and let the leeks do their own thing.
I cut the chicken broth back to about a half cup to reduce the amount of liquid, and also add a few Tbsp. of heavy cream at the end just before the chicken is re-added to the pan to warm up. Doesn't add a lot of calories, and gives a nice creaminess to the sauce.