In a medium saucepan, combine fresh orange juice and sugar, heating over medium heat until the sugar dissolves—about 2-3 minutes. Remove from heat and sprinkle gelatin over the mixture, whisking until completely dissolved. Pour into molds or jars and allow to cool for 30 minutes before refrigerating for at least 2 hours to set firmly.

In a small saucepan, warm the heavy cream over low heat until steaming but not boiling. Remove from heat, stir in vanilla extract and sugar, and mix until well combined. Slowly sprinkle in the gelatin, whisking constantly until completely dissolved.

Once the orange layer has set, carefully pour the vanilla cream mixture over it, ensuring even coverage. Return the assembled jelly to the refrigerator and chill for an additional 2 hours.

To serve, remove from the refrigerator and optionally top with whipped cream and fresh orange slices.