Prepare Ingredients: Peel and dice the turnips and celery root into uniform pieces.
Cook: In a large pot, bring water to a boil. Add the turnips and celery root. Cook for about 15-20 minutes, or until tender.
Drain and Mash: Drain the cooked vegetables and return them to the pot. Mash until smooth or use a food processor for a finer texture.
Season: Season with salt, pepper, and a dash of olive oil or butter if desired. Mix well.
Serve: Use as a substitute for parsnips in your favorite recipes like soups, stews, or as a side dish.