Step 1In a large Mason jar or sealable container, combine the coffee and water, giving it a good stir. Cover and set aside for 12 hours to give the coffee time to infuse. Strain the coffee using a coffee filter, double layer of cheesecloth or tea towel. Taste and sweeten the granita base as desired with simple syrup.
Step 2Pour the granita base into a large, sealable plastic bag or cake pan and freeze. When the liquid begins to freeze, after about an hour, give the bag a good squeeze or scrape a fork repeatedly across the freezing brew in the pan. Repeat every hour until you have icy granules.
Step 3Serve the granita with the heavy cream.