A mirabelle is a delicious little plum that is about the size of a quarter in diameter. Sometimes, although these don't, they have a red blush.
Lorraine is the region of France best known for its mirabelles, especially the cities of Metz and Nancy, which both have their own varietals ... and festivals celebrating the mirabelle (Metz even has a Miss Mirabelle!). In fact, the "Mirabelle of Lorraine" has something called an Indication Géographique Protégée which says that only mirabelles grown in a specified list of cities, towns and villages can be called Mirabelles of Lorraine (kind of like the AOC label on wine, but with seemingly fewer restrictions). The list of towns in the "appelation" is determined by, among other factors, historical references dating from the 16th century about the place of the mirabelle in literature and in texts on local gastronomy.
They ripen in August and are still quite tasty in early September, although I haven't seen any in the markets for a couple of weeks now. They are extremely flavorful. Put that colander of mirabelles on the table next to you and you will smell apple-vanilla-plummy goodness without even sticking your nose down next to the fruit. They're unbelievable.
The one area where they don't excel, at least not the ones we have tried, is in texture: they're often a little mealy (for me). But you don't notice that at all when they're made into the jam. I guess technically what James made is a compote because it's just cooked down mirabelles, lemon juice and a little sugar, but we eat it like jam. And by "like jam" I mean out of the reused Bonne Maman jar, by the heaping spoonful.
Or you can do things the more traditional way and eat it on bread.