Coat a pan with cooking spray and saute shallots until soft (not brown) moistening with wine if necessary

dissolve the arrowroot in 1/2 cup of the chicken broth. Set aside

add remaining wine to shallots and reduce by half. Add remaining chicken broth and reduce by half again.

Add the arrowroot mixture. Transfer the mixture to a food processor and puree until smooth

Return the sauce to the pan. Add lemon juice and lemongrass and simmer over low heat for about 30 minutes, until thick. Strain out the lemongrass and stir in the dill