- 1/4 cup (1/2 stick) unsalted butter
- 1 1/4 pounds yellow onions, thinly sliced (about 4 cups)
- 3 ribs celery, chopped (about 1 cup)
- 1 teaspoon salt
- 1/4 teaspoon cayenne
- 1/8 teaspoon freshly ground black pepper
- 1/4 pound assorted exotic mushrooms, such as shiitakes, chanterelles, and oysters, wiped clean and chopped (about 1 1/2 cups)
- 4 bay leaves
- 3 tablespoons chopped garlic
- 10 cups Chicken Stock 
- 1 1/2 pounds baking potatoes, peeled and diced (about 4 cups)
- 1/4 cup heavy cream
- 2 tablespoons white truffle oil
- Truffle Mushroom Dumplings 
- Fried Parsley 
- Shaved black truffles for garnish
- Melt the butter in a 6-quart stockpot over medium-high heat. Add the onions, celery, salt, cayenne, and black pepper and cook, stirring, until the vegetables are very soft and lightly golden, about 8 minutes. Add the mushrooms, bay leaves, and garlic and cook, stirring, for 2 minutes. Add the stock and potatoes and bring the mixture to a boil. Reduce the heat to medium and simmer, uncovered, until the potatoes are very soft and the mixture is thick and creamy, about 1 hour and 15 minutes.
- Remove the soup from the heat. Discard the bay leaves. With a handheld emersion blender, puree the soup until smooth. Slowly add the cream and truffle oil. Stir gently to blend.
- Ladle the soup into individual bowls, add two dumplings to each bowl, and top with the fried parsley and shavings of truffle, if you wish.