My friend’s brother-in-law, grateful for my friend’s help, gave him the liver of one of his sheep. In turn, my friend passed the liver onto me. So, I wanted to do something different from the traditional liver with onions. (Sorry, Mom.)
I found the recipe for calf’s liver with sorrel sauce in one of my favorite Spanish cookbooks, The Foods & Wines of Spain, by Penelope Casas. Casas mentions that this dish, originating in Segovia, was traditionally made with rhubarb leaves. Rhubarb leaves, despite being toxic, have a very pleasant citrus taste. (I had to take a pinch just to see.) However, due to their known poisonous properties, Casas uses sorrel, instead. Since they are in the same plant family–Polygonaceae–and very closely related, they share similar qualities, including that illuminating tartness from all the oxalic acid.
I did make a few modifications to the recipe.