Sour Cream Mushroom Soup

Heat oil in a large heavy saucepan over low heat. Add onion and cook, stirring, until soft and translucent, 5 to 7 minutes. Add tarragon and nutmeg and cook for 1 minute more. Stir in mushrooms, cover pot and steam until the mushrooms exude their moisture, about 5 minutes.

Sprinkle flour over the mushrooms. Increase heat to medium and cook, stirring, for 3 to 4 minutes. Gradually stir in broth, stirring and scraping any flour that clings to the pan. Simmer, stirring occasionally, until thickened and smooth, 5 to 7 minutes.

Combine sour cream and milk; whisk into the mushroom mixture. Season with salt, pepper and cayenne (or Tabasco), if desired. Gently heat, stirring, until the soup is hot but not boiling. Garnish the soup with chives and tarragon before serving if desired.