Make a custard of the following ingredients: sugar, egg yolks, lemon juice, and grated rind of lemons. The custard should be cooked over water until it coats a spoon. Dissolve gelatin in cold water. Add to custard the dissolved gelatin. In a bowl, beat 6 egg whites very stiff and add gradually 3/4 cup sugar. Pour the lemon custard into egg whites. Tear into bite size pieces one large angel food cake then fold into above mixture lightly with two forks. Grease 8 x 12" baking dish with salad oil and pour mixture into dish. Place in refrigerator and leave overnight. Before serving, ice with whipped cream. (Remove from refrigerator one hour before serving)