Granita is an Italian ice dessert with a crystalline texture. You can substitute espresso in this recipe with two cups very strong brewed coffee, although the flavor will not be as intense.
Place espresso in a medium heat-proof bowl, and pour the hot water over it. Let stand to extract as much flavor as possible without becoming bitter, about 30 minutes. The brew should be very strong; it will be diluted with the simple syrup.
Strain through a fine mesh sieve into a deep-sided 9-by-12-inch metal baking pan, and discard espresso grounds. Add simple syrup, and stir until it is well combined. Place in the freezer, uncovered, until mixture is nearly set, at least 4 hours, whisking it every hour.
Remove mixture from freezer, and scrape surface with the tines of a fork until it is the texture of shaved ice. (If necessary, the mixture can be frozen overnight without whisking; remove it from freezer in the morning, and let sit at room temperature about 10 minutes to allow it to soften before scraping.) Serve.