Soften gelatin in 1/4 cup milk; set aside.
Combine remaining 1 cup milk, egg yolks, sugar, cinnamon, sweet potatoes, and raisins in top of a double boiler, mixing well. Bring water in bottom of double boiler to a boil. Cook, stirring constantly, 10 minutes or until thickened. Remove from heat, and add gelatin mixture; stir well. Chill until slightly thickened.
Beat egg whites (at room temperature) until soft peaks form. Gently fold into sweet potato mixture. Spoon filling into pastry shell. Chill. Garnish with whipped cream before serving.