This chunky mash has a clean earthy taste enhanced by sweet garlic and tangy buttermilk. Even if you've seldom cooked with root vegetables like celery root or rutabaga, don't hesitate to try this recipe - it's delicious!
Make Ahead Tip: Prepare through Step 2 and refrigerate for up to 2 days.
Reheat in a double boiler and stir in the remaining butter and chives (Step 3) just before serving.
