In a medium-sized mixing bowl, whisk together the lemon juice, mustard and creme fraiche. Set aside.
Brush excess dirt off of the roots. Cut off the bottom and top of the roots. Cut the roots into quarters and peel. Rinse in cool water if there is any remaining dirt or debris. Slice each quarter on a mandoline into 1-inch long matchstick pieces and transfer directly to the dressing. Add the salt and pepper and stir well to combine. Cover and place in the refrigerator for a minimum of 1 hour and up to 3 before serving.