Step 1In a medium saucepan, combine the grapes, 1 cup of the wine, the black pepper, cloves and sugar and bring to a boil over high heat. Reduce heat and simmer 3 minutes. Remove from the heat and stir in the remaining wine. Strain through a cheesecloth-lined fine-mesh strainer, pressing the grapes with the back of a wooden spoon to extract any juice. Discard grapes.
Step 2Place the mixture in a wide, shallow glass baking dish and cover loosely with foil. Place the dish in the freezer, and leave it 2 to 3 hours until the granita freezes solid. Before serving, place the frozen granita in the refrigerator to soften slightly. To achieve a slushy texture, scrape the granita with a fork into serving bowls. Serve immediately.