Whisk soy, sugar, ginger, vinegar, oil and cornstarch in saucepan; cook, stirring, until glaze thickens, 2 minutes.
Place chicken, skin side up, on rack in baking pan. Brush with some of glaze.
Bake in 350 degree F oven 45 minutes (until 170 degrees F), brushing with glaze every 10 minutes. Stop glazing 5 minutes before end. Broil chicken 5 minutes to crisp skin.
Fix couscous following package directions; with water, add peas, water chestnuts. Put on platter with chicken. Makes 6 servings.