Elaine, it was cream of sorrel. Here is the recipe--it can also be made with watercress.
The main change I make is to use leeks instead of onions, lots of them, and cook them down very slowly first--for as long as an hour, before adding the flour and continuing with the recipe.
But with the quick saute of onions called for it is a very easy and fast recipe.
I have tons of sorrel in my garden so I make this in quantity and freeze some before adding the egg yolks and cream.
I've also made Swiss chard soup this way, leaving out the flour because the chard stems thicken the soup. Chop them and add them first to the stock until tender, then add the greens.
