Preheat your oven at 150°C (302°F). Butter a baking pan and put a layer of stoned dried prunes.
Bring the milk to a boiling point. In a bowl, whisk the eggs and sugar until pale and thick. Add the flour. Mix well. Add the rum.
Pour the boiling milk on the mix. Whisk thoroughly.
Pour this in the pan.
Cook for 30 minutes.
When finished, turn off the oven, open the oven door a little and leave the clafoutis inside for 15 more minutes.
When cold, cut the clafoutis.
Serve with custard and Chantilly.