Combine lemongrass, lime, lemon, sugar and salt in a large pot
Bring to a boil and reduce head, allow to simmer for 20 minutes
Pour into individual serving dishes and let set

Soften gelatin in cold water
Heat simple syrup and passion fruit together then whisk in gelatin
Let cool and pour on top of set panna cotta

Coconut Foam
1 ¼ cup milk
1 ¼ cup cream
¾ cup simple syrup
½ can coconut milk

In blender, blend all the ingredients together
Skim off top foam and use as garnish