Horseradish gives your vegan Russian dressing a nice kick, and it's important that you use the right kind: prepared horseradish, which comes in a jar. At most grocery stores, it will be in the section with the pickles and other preserved vegetables. Prepared horseradish comes in a jar, and there are white and purple varieties available. Either one will work in this recipe. Purple horseradish just contains beets and beet juice, so it's slightly sweeter than the white kind. That bit of extra sweetness won't hurt your results at all. When you're shopping for horseradish, make sure you don't get horseradish sauce or one prepared with cream or other dairy ingredients. Ideally, you'll be able to find a jar with just horseradish, vinegar, and salt. Other additives are fine, as long as they don't add flavor. Some jarred horseradishes contain preservatives, which won't impact the flavor of your dressing.