Sprinkle sugar evenly into a 10-inch cast-iron skillet; place over medium heat. Cook, stirring constantly, with a wooden spoon until sugar melts and turns golden brown. Gradually add butter and whipping cream, stirring constantly, until mixture is well blended. Remove from heat, and set aside to cool.
Beat egg yolks in a large mixing bowl until thick. Gradually pour cooled caramelized mixture into yolks, adding alternately with flour and salt. Beat well after each addition.
Beat egg whites (at room temperature) and salt until stiff peaks form. Gently fold into caramelized mixture.
Pour mixture into a lightly greased 1-quart casserole. Place casserole in an 8 - inch square baking pan, and fill with boiling water to a depth of 1 inch. Bake at 375° for 45 minutes. Spoon pudding into individual serving bowls, and garnish with a dollop of whipped cream, if desired. Serve hot or cold.