Combine cream and sugar in medium saucepan and bring to boil over medium heat. Continue to boil, stirring frequently to dissolve sugar. If mixture begins to boil over, briefly remove from heat. Cook until mixture is reduced to 2 cups, 8 to 12 minutes.
Remove saucepan from heat and stir in cranberry juice. Let sit until mixture is cooled slightly and skin forms on top, about 20 minutes. Strain through fine-mesh strainer into bowl. Divide mixture evenly among 6 individual ramekins or serving glasses. Refrigerate, uncovered, until set, at least 3 hours or up to 2 days (if chilling for more than 3 hours, cover each ramekin).
Pulse graham crackers in food processor to fine crumbs, about 15 pulses. Melt butter in 10-inch nonstick skillet over medium-low heat. Stir in graham cracker crumbs, sugar, and salt. Cook, stirring frequently, until fragrant, about 1 minute; transfer graham cracker topping to small bowl. (Store at room temperature for up to 3 days.)
When ready to serve, uncover possets, if needed, and let sit at room temperature for 10 minutes. Divide graham cracker crumbs evenly among possets and serve.
