I left out the mustard and nutmeg, didn't do a special garnish, and just used regular cremini mushrooms.
I did crisp up the sage at the beginning and would do it again to get the flavour into the butter, I love crispy Sage but it did not work on top of this soup. I just cooked small pieces of Sage into the soup.
I doubled the recipe except for the wine (only used one cup).
It turned out perfectly!
