Celery root is also known as celeriac; this creamy puree is an excellent accompaniment to Cumin-Crusted Sea Bass.
Place celery root and potato in separate small saucepans. Add water to cover and season with salt. Bring to a boil, reduce heat to medium and cook, covered, until very tender, 10 to 15 minutes for potato, 20 to 25 minutes for celery root. Drain well.
Place the celery root and potatoes in a food processor and blend until smooth, adding milk, if necessary, to achieve a creamy consistency. Stir in oil and season with salt and pepper. Serve hot.
Make Ahead Tip: To keep puree hot for up to 1 hour, set the serving bowl over a wide, shallow pan of barely simmering water and place a piece of parchment or wax paper on the surface of the puree.
1 starch, 5 vegetable, 1 fat