Celery Root Bisque with Walnut Gremolata

Source: Epicurious and Food and Wine

We will serve this first, like an appetizer, in small ramekins.  People can top the soup themselves with the Gremolata.  If you like the idea, you could bring other toppings for the soup, like bacon, croutons and cheese, and people can doctor their own soup to their tastes. Let me know if you have any questions.

Ingredients

Bisque

1/4 cup (1/2 stick) butter
1 cup chopped celery
1/2 cup coarsely chopped shallots (about 3 large)
2 pounds celery roots (celeriac), peeled, woody parts trimmed and discarded, cut into 1/2-inch cubes (about 5 1/2 cups)
1 10-ounce russet potato, peeled, cut into 1-inch pieces
5 cups low-salt chicken broth
1 1/2 teaspoons minced fresh thyme
1/4 cup whipping cream
Additional chopped fresh thyme

Walnut Gremolata

1/4 cup freshly grated Parmigiano-Reggiano cheese

1/2 cup walnuts 

1/4 cup extra-virgin olive oil 

1/2 cup coarsely chopped parsley

Method

Soup

Melt butter in heavy large pot over medium heat. Add celery; cover and cook until slightly softened, about 3 minutes. Add shallots; sauté uncovered 3 minutes. Stir in celery root cubes and potato, then broth and 1 1/2 teaspoons thyme. Increase heat to high; bring to boil. Reduce heat to medium-low, cover, and simmer until vegetables are very tender, about 40 minutes. Cool slightly.

Working in batches, transfer soup to blender and puree until smooth. (Can be prepared 2 days ahead. Cool slightly. Cover and refrigerate.)

Stir cream into soup and bring to simmer. Season to taste with salt and pepper. Ladle soup into bowls. Sprinkle with additional chopped thyme and serve.

Gremolata

Preheat the oven to 375°. Spread the walnuts in a pie plate and toast for 5 to 7 minutes, until golden. Let cool, then finely chop and transfer to a bowl. Add the oil, parsley and grated cheese and mix well.