In a medium saucepan over low heat, warm the pomegranate juice, 2 1/2 cups of water, the vanilla pod and seeds, orange zest, cinnamon stick and salt. Simmer the juice, being careful not to boil. Whisk in the chocolate, sugar and cocoa powder until just melted and dissolved.
Remove the pan from the heat and allow to steep, about 30 minutes. With a strainer, remove the vanilla pod, orange zest and cinnamon stick. Set aside and allow the mixture to come to room temperature.
Place a 2-quart stainless steel, porcelain or plastic container in the freezer. The container should have at least 1 1/2 to 2-inch sides. Pour the mixture into the dish and set a timer for 1 hour.
With a fork, stir the mixture making sure to scrape all the edges (they freeze first).
Allow to freeze. After 30 minutes, while the granita is in the freezer, stir and break up the large chunks. Continue to do this every 30 minutes until the mixture becomes large ice crystals. This may take up to 2 1/2 hours. Once completely icy, transfer the granita to an airtight container. This will keep up to one week. Garnish with pomegranate seeds.