In an electric mixer, beat the egg yolks with the sugar until thick and lemon colored. Slowly add the bourbon and cognac, while beating at a slow speed. Chill several hours. Add the salt to the egg whites and beat until almost stiff, or until the beaten whites form a peak that bends slightly. Whip the cream until stiff. Fold the whipped cream intothe yolk mixture, then fold in the beaten egg whites. Chill one hour. When ready to serve, sprinkle the top with freshly grated nutmeg. Serve in punch cups with a spoon. If desired, add one or two cups of milk to the yolk mixture for a thinner eggnog.