In a large bowl, dissolve gelatin in the 1 cup of boiling water. Stir in lemon peel, lemon juice, and 3/4 cup cold water. Chill, until partially set.
When, partially set, add unbeaten egg whites to gelatin mixture. Beat with electric mixer, until mixture is light and fluffy. About 1-2 minutes.
Pour mixture, into eight 5 oz. custard cups. Or, other cups. (If other cups, are bigger, your servings may be reduced to approximately six.) Chill, until firm. (Slight separation, into layers, may occur.)
Meanwhile, in saucepan, crush 1/2 cup of the blueberries. Blend together cornstarch and 1/2 cup cold water. Add cornstarch mixture and sugar to crushed berries. Stir.
Cook, over medium heat, stirring constantly, until mixture is thick and bubbly. Then, cook 1 minute longer.
Remove from heat, stir in remaining berries and vanilla. Cool, then chill sauce, in refrigerator.
When ready to serve, remove gelatin cups, as many as needed. And, top with chilled blueberry sauce.(May top with whipped topping, if desired.)