This recipe is my adaptation of Patricia Well’s Soupe aux Deux Céleris from Bistro Cooking.

If you prefer a smooth soup with no crunchy bits, sweat all the celery along with the leeks.

For a winter-holiday meal, I garnish each serving with crème fraîche, salmon roe, and chopped chives. Most other times, I opt for a sprinkling of chopped pale green celery leaves, which are lovely on the pale green soup. A bit of chopped parsley does the trick nicely, too.

Steps

1. Melt the butter in a large Dutch oven over medium heat and heat until the foaming subsides. Add 2½ cups of the chopped celery ribs, leeks, celery seed, thyme, bay leaf, and 1½ teaspoons salt. Stir to coat, cover, reduce the heat to low, and continue cooking, stirring occasionally, until the leeks and celery have released their juices, about 10 minutes. Add the celery root, broth, and 1 quart of water, increase the heat to medium-high, and bring to a boil. Reduce the heat to low, cover, and simmer until the celery root is very tender, 15 to 20 minutes. Discard the bay leaf.
2. Purée the mixture in a blender (or with an immersion blender) working carefully and in batches, if necessary, until smooth. Return the puréed mixture to the pot, if necessary, add the reserved 1½ cups of chopped celery, and heat over medium-low, stirring occasionally, until the celery is just tender and the soup is heated through, about 5 minutes. Taste and adjust the seasoning with additional salt, if necessary, and pepper to taste. Serve at once, garnishing each portion as desired.