This is a basic recipe with only a handful of ingredients, but it certainly has lots of flavour. The twist in the taste comes from the roasting of the mushrooms. The soup could be made without roasting at all, by chopping the mushrooms and stewing them with the onion and potato instead. However, the mushrooms become very watery and lose their good, strong taste.
I like to save one or two of the roasted mushrooms and chop them for the garnish, along with some chopped tarragon or pars