How to Make It
In a blender, puree the drained lychees until smooth. Add 1 cup of the heavy cream and puree until smooth. Strain the lychee puree through a fine sieve set over a medium bowl, pressing hard with the back of a spoon to extract as much of the puree as possible.
In a small bowl, sprinkle the gelatin over the water and let stand until softened, about 5 minutes. Scrape the gelatin into a small saucepan. Add the granulated sugar and the remaining 1 cup of cream and cook over very low heat just until the sugar is dissolved, about 2 minutes. Let cool completely, then whisk in the lychee puree. Pour the panna cotta into 8 Champagne flutes and refrigerate them until they are set, about 4 hours.
Meanwhile, in a small bowl, whisk the egg white until frothy. Using a pastry brush, lightly brush the basil leaves on both sides with the egg white, then sprinkle them all over with the superfine sugar. Shake off any excess sugar and transfer the basil leaves to a wire rack to dry, about 6 hours.
Garnish each glass of panna cotta with a sugared basil leaf and serve right away.
Make Ahead
Notes
Canned lychees in syrup are available in the Asian section of most supermarkets. To shorten the time it takes to prepare this dessert, cool the panna cotta base quickly by pouring it into a stainless steel bowl set over ice water and stirring frequently.