1/2 cup Cinnamon Toast Croutons, for garnish (see Note)
In a small, microwave-safe bowl, sprinkle the gelatin over the water and let stand until softened, about 3 minutes. In a large microwave-safe bowl, whisk the sweet potatoes with the whole milk, heavy cream, condensed milk, brown sugar and salt. Microwave the sweet potato mixture at high power until warm, about 1 minute. Microwave the gelatin mixture at high power until melted, about 10 seconds, then whisk it into the sweet potato mixture and let the panna cotta mixture cool.
Lightly rub six 1/2-cup ramekins with vegetable oil. Pour the panna cotta mixture into the ramekins and refrigerate until firm, at least 2 hours.
In a small bowl, combine the cranberry sauce and cranberry juice. Run the tip of a paring knife around the inside of the ramekins. To unmold, dip a ramekin into a shallow bowl of hot water for 30 seconds; dry off the ramekin and invert the panna cotta onto a plate. Spoon the cranberry sauce on top and garnish with the Cinnamon Toast Croutons.
The panna cottas can be refrigerated in the ramekins for up to 2 days.