The first step for using burdock in recipes in which it will be pickled or marinated is to parboil it. This makes it crisp-tender and ready to absorb flavor-rich sauces and pastes.
Pour the water into a large pot, add the vinegar, and set aside. Have ready a large bowl of ice water and a colander.
Cut the unpeeled burdock into slices on the diagonal or into matchsticks, depending on the recipe you will be using. As soon as the burdock is cut, add it to the vinegar water to prevent discoloration.