Wrap 8 1 to 1 1/2-cup ramekins with an 8-10 inch tall parchment collar. * The collar should extend above the rim of the ramekin by at least 6 inches, so that the finished mousse will set a couple of inches above the rim, making it look like a souffle.
Prepare an ice bath by putting ice and cold water in a large bowl or pan that is larger than the sauce pan you'll be using.
Pour 1/2 a cup of cold water into a sauce pan and sprinkle with gelatin.
Let stand until gelatin softens and swells (about 5-10 minutes).
Stir in the sugar, salt, lime zest, lime juice and yolks.
Place over medium heat and cook, stirring constantly, until the mixture thickens and the gelatin melts completely (about 6-8 minutes).
Do not allow the mixture to boil.
Set the sauce pan in the ice bath until the mixture is cool to the touch.
Remove the pan and let sit at room temperature.
Combine the cream and icing sugar in a bowl.
Whip until soft peaks form.
Add the lime mixture to the cream with a rubber spatula.
Fold together until smooth.
Pour into prepared ramekins.
Refrigerate until cold and firm.
Remove 20 minutes before serving.
Remove collar and serve.
* This recipe can be substituted with lemons or oranges or grapefruits instead of limes.
* For a unique serving suggestion try hollowing out half of the lime/other citrus and using the empty peeling shell as the serving dish. (in this case, you don't need the parchment collar, just spoon the mousse until it is level with the rim of the peel).