Found this French tale type definition in an essay by Swank about the use of the classical Irish Immram form in C.S. Lewis’ “Voyage of the Dawn Treader.”

“Another tale-type Flieger analyzes is the aventure, a French term referring to “adventures” or “dangerous escapades” in a magical otherworld, “exciting for their own sake, ending in peace and prosperity” […] In aventures, there is a goal, of sorts, but the narrative focus is on the protagonist’s episodic adventures and, particularly in narratives featuring young protagonists, the lessons learned from each episode. As Flieger writes, both the quest and aventure “follow the traditional romance trajectory—a hero’s journey and return,” but the quest is more focused upon the goal, while the aventure is more focused upon the escapades.”

While we’re on the topic, I highly recommend this essay about C.S. Lewis as an Irish writer. He’s usually credited as British, but was born in and retained strong ties to Ireland his whole life.