To make a simple horseradish sauce, peel and chop an 8- to 10-inch long horseradish root into small pieces. Place it into a food processor with 2 tablespoons of water until well ground. Add a tablespoon of vinegar and a pinch of salt to the mixture and drain well.
As homemade horseradish is generally much stronger than the store-bought version, another alternative is to make a horseradish cream sauce, which has a milder flavor. Grate 1/4 cup of fresh horseradish into a medium-sized bowl. Combine the root with 1 cup sour cream, 1 tablespoon Dijon mustard and 1 teaspoon white wine vinegar. Add salt and ground pepper as desired, and whisk until smooth. Place the sauce into a well-sealed container, and leave it in the refrigerator overnight or for at least four hours in order for the flavors to meld. The recipe makes about 4 cups.
When choosing horseradish root at the store, keep in mind that the whiter the root, the fresher the horseradish. Choose roots that are firm and have no green or soft spots. Horseradish is available all year, although spring is its prime season. Homemade horseradish and sauce lasts three to five weeks when stored in the refrigerator.