2 tbsp. (1/4 stick) unsalted butter
1 med. onion, coarsely chopped
1 lg. shallot, coarsely chopped
2 very lg. leeks, carefully washed & cut into 1" rings (with some green)
1 rib celery, coarsely chopped
2 med. baking potatoes, peeled and cut into med. cubes (about 3 c.)
1 sm. celery root, peeled & cut into med. to sm. cubes (about 1 1/2 c.)
1 tsp. salt
1/2 tsp. white pepper
4 c. rich Chicken Stock, heated

Melt butter in a deep saucepan and saute onion and shallot over medium heat until onions begin to turn brown, about 5 minutes. Add leeks and celery. Cover tightly and sweat for 15 minutes over very low heat.

Add potatoes, celery root, salt, pepper and 1 1/2 cups of the stock to the saucepan. Bring to a boil and simmer, uncovered, for 10 minutes or more, until potatoes and celery root are fork-tender.

Transfer soup mixture to a food processor and puree until smooth. Return to the saucepan and add the balance of the stock. Simmer for a few minutes, then correct seasoning if necessary. Serve medium hot. Serves 6.