In a small bowl, whisk together 1/4 cup grated horseradish, the crème fraîche or sour cream, lemon juice, and chives, if using, until combined. Season with salt and, if desired, up to 1/4 cup more horseradish to taste. (You can cover and refrigerate the horseradish cream for up to 3 days. You may need to stir the sauce to recombine before serving.)