Black Truffle Soup

2 tablespoons unsalted butter

1 cup chopped peeled celery root
1/4 cup sliced leeks (rinsed well)
3/4 cup parsnips, chopped roughly
1 lb. boiling potatoes, peeled and chopped roughly
1 thyme sprig
1/4 teaspoon salt
1 cup water
1 cup chicken broth, preferably homemade
1 1/2 oz. black truffle

1/2 cup heavy cream
salt and freshly ground black pepper

Melt butter in saucepan over medium heat. Add celery root, leek, parsnips, potatoes, thyme sprig, salt and water. Simmer, covered, for 10 to 15 minutes or until almost all the liquid is gone. Stir in the broth and simmer, covered, for 15 minutes. Puree mixture in a blender until smooth, or use a handheld blender. Clean and peel truffle(s). Mash in a bowl and add to the soup along with the heavy cream. Adjust seasonings to taste with salt and freshly ground black pepper.

[The thyme garnish shown here is thymus serpyllum, a creeping thyme I wintersowed this year and is growing very nicely in the garden.]