This is not actually a separate variety of lentils. They are green lentils, grown from Ancia lentil seeds, which a group of French farmers started growing in 1994 and to which a fancy, trademarkable name was applied. Some feel the taste is reminiscent of chestnuts.
They are grown in the départements of France called “l’Indre” and Cher, which are pretty much in the centre of France, in a region called the Berrichonne plateau or country.
Language Notes
Berry is the old name of a province of France, that used to take in today’s départements of l’Indre and neighbouring Cher.