Rinse the berries, drain and roll them on paper towels to dry. Hull the berries and trim any bruises and hard, underripe shoulders and tops. Purée in a blender to smooth. Press the purée through a fine mesh strainer yielding approximately 3 cups of purée (estimate ½ cup per person). Taste the purée and add the necessary amount of sugar and a pinch of salt. Note: Adding a lot of additional sugar will make finer crystals, more like a sorbet, and the freezing will be different. You would need to use an ice cream machine.
Test the granita base by freezing 1 tablespoon of the purée on a wide glass (Pyrex is fine) or stainless steel pan. Once the purée forms an ice chip, taste. Adjust the sweetness accordingly with the remaining purée and your remaining sugar.
Pour the purée into the pan, up to 1 inch deep. Cover and freeze. After 1 hour, the purée should have a thick crust. Remove the purée and chop the thick crust with a knife, fork or pastry knife combining the unfrozen with the frozen top. Cover the pan and return to the freezer. Check the granita every 30 minutes, chopping the frozen crystals until it becomes a consistent flaky mass for an additional 2 hours. Note: If it forms a frozen block, let it thaw a bit and start over.
Transfer the granita to a chilled container, cover and keep frozen. Freeze the dessert dishes before serving (wine glasses and goblets look great) and serve with fresh berries, sprig of mint or your favorite cookie.