Preheat oven to 300 degrees F.
Shred parsnips and celery root. Combine egg whites, flour, chives, mustard, salt, pepper and baking powder in a large bowl. Stir in the shredded vegetables.
Heat 2 tablespoons oil in a large skillet over medium heat. Cook 4 pancakes per batch, using about ¼ cup of batter for each. Cook until golden, 2 to 3 minutes per side. Keep warm in the oven. Repeat for 3 more batches, using 2 tablespoons oil for each batch. Serve topped with crème fraîche (or sour cream) and chives, if desired.
