This is what you do when life gives you unripe grapes. Made with wild or domestic grapes, verjus (verjuice) is just the strained juice of unripe grapes. You use it like a mild vinegar. Best part? Verjus plays well with wine, where vinegar does not.
A great thing to do with second grade fruit you might have going to spoil in your kitchen. We all do it buy beautiful fruit get busy, and forget to eat it. Now you don't have to lose it just save it! :)