- 1 1/2 teaspoons canola oil
- 1 large onion, chopped
- 1 1/2 teaspoons chopped fresh tarragon
- 1/4 teaspoon freshly grated nutmeg
- 1 pound mushrooms, trimmed and sliced
- 1/2 cup all-purpose flour
- 3 1/2 cups reduced-sodium beef broth
- 1 cup reduced-fat sour cream
- 1 cup low-fat milk
- Salt and freshly ground pepper to taste
- Pinch cayenne pepper (optional)
- Snipped fresh chives to garnish (optional)
- Fresh tarragon sprigs for garnish (optional)
- 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.