Step 1

Bring wide strips of lime zest, salt, ½ cup sugar, and 2 cups cream to a boil in a medium saucepan over medium-high heat. Reduce heat and simmer, swirling pan occasionally and being careful not to let mixture boil over, until cream is slightly thickened, about 5 minutes. Remove from heat and stir in lime juice. Strain mixture through a fine-mesh sieve into a large measuring glass; divide among 4 small glasses, bowls, or 8-oz. ramekins. Chill until custards are no longer warm, about 30 minutes, then cover with plastic wrap and continue to chill until set, at least 2 hours.

Step 2

Just before serving, whisk remaining ½ cup cream in a small bowl to soft peaks; whisk in remaining 1 Tbsp. sugar.

Step 3

Top each custard with dollops of cream, a few lychees (you may have a few left over), and some finely grated lime zest.

Step 4

Do Ahead: Custards can be made 2 days ahead. Keep chilled.