Serves 20

1. Mix the sugar and milk and bring to a boil. Lower the heat immediately and continue to simmer [soft boil] for 1 hour. Add the vinegar and stir until it becomes thick. Strain the milk and pour it into a container, either glass or aluminum or ceramic. 
2. Allow to cool completely, when cooled and solid, cut into diamond shapes. Lift the pieces out of the tray and roll and dust the top with the finely-ground pistachio. Serve.