In a medium saucepan, combine the water and brown sugar over medium heat. Stir frequently until the sugar is completely dissolved in the liquid. You should have a clear syrup at this point.
Once the sugar is dissolved, add in the freshly grated ginger, ground cinnamon, nutmeg, allspice, molasses, vanilla extract, and a pinch of salt. Mix well to ensure all ingredients are evenly distributed.
Allow the mixture to come to a gentle simmer and let it cook for approximately 5 minutes to enhance the flavors. After simmering, remove the saucepan from heat and let the mixture cool completely at room temperature.
When the mixture has cooled, strain it through a fine mesh sieve into a shallow dish to eliminate the ginger pieces for a smoother texture. This step is crucial for achieving a refined granita.
Place the shallow dish filled with the strained mixture in the freezer and freeze for about 2 hours without stirring.
After 2 hours, take the dish out of the freezer and use a fork to scrape the mixture vigorously, creating fluffy ice crystals that will form the granita texture.
Return the dish to the freezer and repeat the scraping process every 30 minutes for an additional 2-3 hours. This will ensure the granita achieves a light and flaky consistency, perfect for serving.
Once completely frozen, serve the granita in chilled glasses, and for an added touch, garnish with a light sprinkle of ground cinnamon or fresh mint leaves to enhance the presentation and flavor.
Notes
For a smoother texture, be sure to strain the mixture well.