For the flambéed litchis, peel the litchis, cut them in half and remove the seeds.
Put the sugar in a pan with three tablespoons of water and heat until brown, thick caramel. Add the lychees and stir the whole thing for 5 minutes.
In an iron pan, heat the rum, pour it to the caramel and flambé immediately.
Serve the flambéed lychees in a mug, with 2 balls of vanilla ice cream if desired.