Dissolve gelatin in cold water for about 5 minutes, then gently warm until fully dissolved.

In a chilled bowl, whip heavy cream on high speed for 3-5 minutes until stiff peaks form. Refrigerate.

In another bowl, whisk egg yolks, granulated sugar, and salt for 5-7 minutes until pale and slightly thickened. Stir in vanilla extract.

Carefully fold the cooled gelatin into the egg mixture until well combined.

Fold in one-third of the whipped cream to lighten the mixture, then gently add the remaining whipped cream until no white streaks remain.

Transfer the mousse to cups or a bowl, cover, and refrigerate for at least 3 hours to set.