Cut each berry into quarters; you should have about 2 cups lightly packed fruit. In a food processor, combine the strawberries and sugar and process until smooth, about 1 minute. Transfer the puree to a medium bowl. Add the water and vinegar and stir well to combine.

Pour the base mixture from one of the recipes at right into a 9-inch-square shallow baking pan. This pan size works best because it provides a large surface area, a key point in speeding up the freezing process. To further hasten freezing, use a metal pan (metal conducts cold well).

Put the pan in the freezer and stir every 30 minutes, being sure to scrape the ice crystals off the sides and into the middle of the pan, until the mixture is too frozen to stir, about 3 hours, depending on the individual recipe and on how cold your freezer is (some granitas can freeze in as little as 1 hour). Use a large dinner fork to stir and scrape; the tines are perfect for breaking up ice crystals.

Cover the pan with plastic and freeze overnight. When ready to serve the granita, place a fork at the top of the dish and pull it toward you in rows, moving from left to right and rotating the pan as well. Scrape up the shaved ice and serve in chilled glasses or bowls.