Nutrition per serving may change if servings are adjusted.
4 cups low-fat milk
3 cups water
3 pounds celery root, peeled (see Tip) and cut into 1-inch cubes
2 tablespoons unsalted butter, softened
1/2 teaspoon sea salt
Freshly ground pepper to taste
Bring milk, water and celery root to a simmer in a large saucepan over medium heat. Reduce the heat to maintain a gentle simmer and cook until very tender, about 30 minutes. Reserve 1 cup of the cooking liquid, then drain.
Puree the celery root, butter, salt and pepper in a food processor (or blender) until smooth and the consistency of thinned mashed potatoes. Add some of the reserved cooking liquid, if necessary, for the right consistency.
Make Ahead Tip: Cover and refrigerate for up to 2 days; gently reheat on the stovetop, adding a little milk or water, if needed.
Tip: To peel celery root, remove the thick skin with a knife or use a vegetable peeler and peel around the root at least three times to make sure to remove the layer of the fibrous skin.