Make Ahead Tip: Cover the puree with parchment paper or foil and keep warm over a pan of barely simmering water for up to 1 hour. (Alternatively, cover and refrigerate for up to 2 days; reheat in the microwave.)
Look for round celeriac globes with smooth, tight, papery skins. Fewer indentations mean easier peeling. But do clean out whatever indentations there are.
1 starch, 2 vegetable, 1 fat