Peel or use a sharp knife to remove the exterior of the root. Cut into chunks.

Add to food processor fitted with the steel blade and using on/off motions pulse until the horseradish is finely grated. With the machine running add 5 T of vinegar and the salt through the feed tube. Pulse until mixture has come together but is not pureed.

Averting your eyes and mouth, carefully remove the processor lid and scrape 2/3 of the mixture into a clean glass jar. To the horseradish still in the processor add the beet and pulse again. Remove that to a clean jar.

Taste for salt and vinegar and add sugar if that's what you like. Tamp the mixture into your jars and then drizzle more vinegar on top. Cover with a piece of plastic wrap and place the lid on tightly. Immediately place in the refrigerator.