Bloom the gelatin: Sprinkle the unflavored gelatin over the cold water in a small bowl and let it sit for 5 to 10 minutes.
Heat the milk: In a medium saucepan, combine the whole milk with half of the granulated sugar and add the split vanilla bean. Heat until steaming.
Temper the eggs: In a separate bowl, whisk the egg yolks with the remaining sugar. Gradually add about half of the hot milk mixture to the yolks, whisking continuously.
Cook the custard: Return the tempered mixture to the saucepan. Cook over medium-low heat, stirring constantly until thickened (about 8-10 minutes).
Strain: Strain the custard through a fine mesh sieve into a bowl and add the bloomed gelatin, stirring until dissolved.
Cool: Allow the custard to cool to room temperature, stirring occasionally (about 15 minutes).
Whip the cream: Whip the heavy cream to soft peaks in a large bowl.
Fold together: Gently fold the whipped cream into the cooled custard until fully combined.
Set: Transfer the mixture into a mold or individual cups and refrigerate for at least 4 hours or until set.
Notes
Store in the refrigerator for up to 3 days. Can be made up to two days in advance.