Soak the 4 sheets of gelatin in cold water. In a saucepan, combine the heavy cream, sugar, and vanilla. Heat over medium-low, stirring constantly, until it just begins to simmer. Remove from heat, add the squeezed gelatin, and stir well until dissolved.

Using a ladle, pour the mixture into small bowls or ramekins. Let cool to room temperature, then refrigerate for at least a couple of hours.

For the gelée, soak the 2 sheets of gelatin in cold water. Scoop out all the flesh from a ripe mango and blend until smooth.

Pour half of the mango puree into a saucepan and heat over low, adding the powdered sugar and juice of half a lime. Stir to combine.

When it just begins to simmer, remove from heat and add the squeezed gelatin, stirring well to dissolve. Add the remaining mango puree and mix. Let cool slightly at room temperature.

Make sure the panna cotta has set, then spoon the mango mixture over each bowl. Refrigerate for another couple of hours. Once chilled, they're ready to enjoy!