Twice-Baked Celery Root Potatoes

Preheat oven to 450 degrees F. Place potatoes in oven, directly on rack, and bake 45 to 50 minutes or until tender when pierced with knife. Remove potatoes from oven and set aside until cool enough to handle. Reset oven temperature to 400 degrees F.

Meanwhile, in 3-quart saucepan, place celery root and enough water to cover; heat to boiling on high. Reduce heat to low; cover and simmer 15 minutes or until celery root is tender. Drain.

In food processor with knife blade attached, blend celery root with milk, margarine, 3/4 teaspoon salt, and 1/4 teaspoon ground black pepper until pureed. Transfer puree to large bowl.

When potatoes are cool enough to handle, cut 1/4-inch slice from both of the narrow ends of each potato, then cut each potato crosswise in half. Stand potatoes on narrow ends. With spoon, scoop potato from skins into bowl with celery root puree, leaving about 1/4 inch of potato with skin and being careful not to break through bottom of potato. Reserve potato-skin cups. With potato masher, mash potato with celery root until almost smooth. Stir in Parmesan.

Spray 15 1/2" by 10 1/2" jelly-roll pan with nonstick cooking spray. Spoon potato mixture into potato-skin cups, mounding slightly. Place cups in prepared pan. Bake 25 minutes or until heated through and lightly browned. (If not baking right away, cover and refrigerate filled potatoes overnight; bake 35 to 40 minutes.) Sprinkle with parsley to serve.