Cut a piece of aluminum foil long enough to fit around a 1- quart soufflé dish, allowing a 1- inch overlap; fold foil lengthwise into thirds. Lightly oil one side of foil and bottom of dish; wrap foil around outside of dish, oiled side against dish, allowing foil to extend 3 inches above rim to form a collar. Secure foil with string or freezer tape.
Beat egg yolks until thick and lemon colored. Add 1/2 cup sugar, butter, 1 tablespoon rum, vanilla, and salt; beat well. Stir in chestnuts.
Beat egg whites (at room temperature) until soft peaks form. Fold into chestnut mixture. Spoon into prepared soufflé dish. Place dish in a 13- x 9- x 2 - inch baking pan; pour hot water into pan to a depth of 1 inch. Bake at 350° for 50 minutes or until puffed and set.
Beat whipping cream in a small mixing bowl until foamy; gradually add 1 tablespoon sugar, beating until soft peaks form. Beat in 1 teaspoon rum.
Spoon hot soufflé into individual serving bowls. Serve immediately with whipped cream topping.