These cones are best made on a flat decorative iron. It is also possible to make them crepe style in a nonstick pan.
Melt the butter and allow to cool.
Beat egg whites until soft peaks appear. Add 1 tablespoon confectioners' sugar and the salt, and whip until stiff. With a wooden spoon, gently fold in remaining sugar and the vanilla. Gradually fold in flour and cooled butter until incorporated.
Heat the iron and rub with a lightly oiled piece of paper towel, then place 1 1/2 tablespoons of batter on it and close the cover. When steam subsides, check to see if wafer is golden brown. Remove it gently with a thin spatula; then, moving quickly, roll the wafer around a paper cone. It will cool and harden almost immediately. Store in an airtight container.