PREPARE THE MANGO LAYER: In a small bowl, sprinkle 2 teaspoons of gelatin over 2 tablespoons of cold water and let it sit for 5–10 minutes to bloom.
HEAT THE MANGO MIXTURE: In a small saucepan over low heat, warm the mango puree and lemon juice until steaming but not boiling. Remove from heat and stir in the bloomed gelatin until fully dissolved.
FILL MOLDS: Pour the mango mixture evenly into ramekins or silicone molds, filling each about halfway. Chill in the refrigerator for 1 to 2 hours, or until the layer is set.
PREPARE THE CREAM LAYER: In a clean small bowl, sprinkle the remaining 2 teaspoons of gelatin over 2 tablespoons of cold water. Let bloom for 5–10 minutes.
HEAT THE CREAM BASE: In a separate saucepan, combine the heavy cream, whole milk, sugar, and vanilla extract. Heat over medium-low, stirring occasionally, just until the sugar dissolves and the mixture is warm. Do not boil.
ADD GELATIN TO CREAM: Remove the pan from the heat and stir in the bloomed gelatin until completely dissolved. Allow the mixture to cool to room temperature, but do not let it set.
ASSEMBLE THE PANNA COTTA: Gently pour the cooled cream layer over the set mango layer in each mold. Refrigerate again for 3–4 hours or overnight until fully firm.
UNMOLD AND SERVE: To unmold, dip the ramekins briefly in warm water for 5–10 seconds, then invert onto serving plates. Garnish with fresh mango slices, mint leaves, passionfruit pulp, or edible flowers if desired.