In a small bowl, beat cream until stiff peaks form. Fold in the horseradish, mustard and salt. Cover and refrigerate for 15 minutes before serving.
Editor's Note: Store fresh horseradish root in a sealed plastic bag in the refrigerator and it should keep for up to 3 months. Take care when grating horseradish, it has more sting than chopping onions. Use a vegetable peeler or paring knife to remove the outer skin from the root.