In a small bowl, sprinkle 1 ½ teaspoons of gelatin over 2 tablespoons of cold water. Let it sit for 5–10 minutes to bloom.

In a saucepan, combine cream, milk, and sugar. Heat over medium heat until sugar dissolves and the mixture is hot but not boiling. Remove from heat and stir in the bloomed gelatin until fully dissolved. Add vanilla extract.

Pour the cream mixture into serving glasses or ramekins, filling halfway. Let cool slightly, then refrigerate for at least 2 hours, or until set.

Bloom the remaining 1 teaspoon of gelatin in 1 tablespoon of cold water. In a small saucepan, heat mango puree, citrus juice, and sugar (if using) until warm. Stir in the bloomed gelatin until dissolved. Let cool to room temperature.

Pour the mango layer over the chilled cream layer. Return to the refrigerator and chill for another 2 hours, or until fully set.