Step 1

Place diced horseradish in a food processor; add a splash of cold water. Pulse on and off until mixture begins to blend. Scrape down sides of food processor container (the fumes are very strong, so keep your face away from the bowl and the room well ventilated).

Step 2

Continue blending, adding a bit more water if mixture seems too dry. Process until horseradish is finely ground. Wait 2 minutes before adding the vinegar and salt; supposedly this makes the horseradish hotter. After 2 or 3 minutes, add vinegar and salt. Continue processing until mixture is smooth and creamy or to your desired consistency, adding more water if necessary. Transfer to airtight storage containers. Refrigerate.