How to Make It
In a medium saucepan, combine the cream with the sugar and makrut lime leaves and bring to a simmer. Cook over moderately low heat, stirring occasionally, until the cream is slightly reduced, about 15 minutes.
Whisk the lime juice into the hot cream. Strain the cream through a fine sieve set over a measuring cup. Stir in the lime zest and salt. Pour the cream into eight 6-ounce glasses and refrigerate for at least 2 hours, until chilled and set. Top the custards with whipped cream, garnish with lychees, mint and sea salt and serve right away.
Makrut lime leaves, popular in Indonesian, Thai and other Southeast Asian cuisines, are available at specialty food stores and online.