Ah yes, sorrel - grew it for the first time this year, and have just noticed it is perennial - is that right? It flowered, and I thought it would behave like spinach beet and die off, but it has since sent up masses of fresh green leaves. I am now expecting it to behave like docks, and live for ever.
I like it folded into an omelette at the last moment, barely wilted. It is a shame it goes such a gloomy khaki colour when cooked, but the omelette and lots of fresh parsley (I agree with you about flat-leaved parsley, of which I have mountains) disguise this.