A puree of parsley and scallions mixed with lemon juice and oil both flavors the couscous and acts as a sauce for the fish. The taste of flat-leaf parsley really comes through if you use the flat-leaf variety. Any mild-tasting fish fillets will go well with the relatively delicate sauce. Try lake perch, whiting, croaker, drum, or bass, or of course, any of the flounder family, such as lemon or gray sole. Variation: Flounder with Basil and Parsley Couscous - Make the herb puree with 1/4 cup fresh basil and 1/2 cup flat-leaf parsley leaves. Wine: Match the tartness of the lemon juice with an acidic white wine. Try a good-quality Soave or Orvieto from Italy. From African Quick From Scratch Fish & Shellfish, Food & Wine.