From my mother:
The sorrel I have is perennial and has grown into a huge plant. I don't know how it stands up to snow and frost but it definitely grows in England. Though I never had it there, it was probably regarded as a poor persons food.
A big bunch of sorrel leaves, stems trimmed off. Wash well.
Potato scrubbed but leave skin on. Chop into cubes and parboil or put in microwave for 4-5 minutes.
Bunch of spring onions chopped fine including greens
3 Cups of vegetable stock
2 tablespoons Olive oil
Nutmeg, salt & pepper
Heat oil, medium, add onions and sorrel leaves, stir and cook for three minutes till leaves turn bright green.
Add potato, vegetable stock, cook for about 6 minutes or until potato is fully cooked.
Grate in nutmeg
Leave to cool a bit and blend til smooth, return to pan to heat through if necessary.
Taste, add salt & pepper to liking.
It has it's own flavor and doesn't taste like anything else.
(The original recipe called for thickening with corn flour but I find potato does just as good a job.)
Oh I also added a large pinch of dry mint with the potato & veg stock.