Place ice, sherry, port, brandy, egg yolks, bitters, and sugar into the bowl of a blender. Blend for a minute until smooth, taste, and add additional confectioner's sugar to taste. Pour into highball glasses, and sprinkle with cinnamon to serve.
This recipe contains raw egg. We recommend that pregnant women, young children, the elderly, and the infirm do not consume raw egg. Learn more about egg safety from our article, Making Your Eggs Safe.