Step 1

In a large saucepan, combine the olive oil and shallots. Cook over medium-low heat until softened, stirring occasionally, about 4 minutes. Add the garlic and cook until soft, about 1 minute. Add the celery root, potato, water to cover, and salt. Bring to a boil, cover, lower to a simmer and cook over medium-low heat until the celery root is very tender, 15 to 20 minutes.

Step 2

Scoop out a cup of the cooking liquid and reserve; drain the cooked vegetables. Puree the celery root mixture in a food processor or blender until completely smooth, adding a bit of cooking liquid, if necessary (I added 1 Tbsp). If you want this to be a little richer, you can add a Tablespoon or 2 of unsalted butter to the food processor instead of the cooking liquid. Taste for seasoning and add a little extra salt if needed. Once I added a little truffle salt and that was delicious! Serve right away or return to the saucepan and keep warm until ready to use. I have also reheated it the next day in a saucepan over gentle heat.