Sprinkle the gelatin over the cold water in a small bowl and let it sit for about 5 minutes.
In a saucepan, combine the orange juice, orange zest, sugar, and egg yolks.
Cook the mixture over low to medium heat, stirring constantly, until it slightly thickens. Do not allow it to boil.
Add the softened gelatin and stir until completely dissolved.
Remove from the heat and stir in the vanilla extract.
Allow the orange mixture to cool completely to room temperature.
In a large mixing bowl, whip the heavy cream with a pinch of salt until soft peaks form.
Gently fold the cooled orange mixture into the whipped cream.
Continue folding until the mixture is smooth, creamy, and evenly combined.
Divide the mousse among six dessert glasses or serving cups.
Cover and refrigerate for at least 3 hours, or until completely set.
Before serving, garnish with whipped cream, orange slices, orange zest, chocolate shavings, or fresh mint.
Serve chilled and enjoy.