(I have to admit that until Chef Debaste sent this recipe to me, I had never heard of verjus. In case it is new to you too, here's what I learned.) Verjus is a tart, fresh non-alcoholic juice pressed from unripe wine grapes – essentially a very young white wine without the alcohol. Verjus, which takes its name from the French term vert jus, which literally means “green juice,” is a culinary ingredient most often used in sauce making. Verjus is available in gourmet food stores, or directly from producers. If you don’t happen to have any verjus sitting around your kitchen, try using a very astringent white wine.