Oil and flour a 9" springform tin. Preheat oven to 300. Beat egg whites and salt at full speed until they stand in peaks. Sift sugar and sprinkle in 1 tablespoon at a time, still beating on high speed. Fold in the vinegar, vanilla, and hazelnuts. Pour into prepared tin and bake at 300 for 1 hour. Turn off heat and leave pan in oven until it is cold. When it is cold, remove it from tin (it will collapse slightly). Before serving, fill the center with vanilla ice cream (you can also used whipped cream), and pour over the chocolate sauce, then sprinkle more chopped hazelnuts on top. Chocolate Sauce 1 large package semi-sweet chocolate, melted in double boiler 1 to 2 tablespoons Cointreau Combine.