Sprinkle the gelatin over cold water and let stand for 5 minutes. In a 3-quart saucepan, warm the cream with the sugar, salt, and vanilla over medium-high heat.
Do not let it boil. Stir in the gelatin until thoroughly dissolved. Take the cream off the heat and cool about 5 minutes.
Put the sour cream in a medium bowl. Gently whisk in the warm cream a little at a time until smooth. Taste for sweetness. It may need another teaspoon of sugar. Rinse 8 (2/3-cup) ramekins, custard cups, or coffee cups with cold water. Fill each one 3/4 full with the cream. Chill 24 hours.
To serve, either unmold by packing the molds in hot towels and then turning each out onto a dessert plate, or serve in their containers. Serve alone or with the fruit, or drizzle each portion with about 1/2 teaspoon artisan balsamic vinegar or saba.
Recipe courtesy of Lynne Rossetto Kasper