Harvard Beets 2 cups Cooked or Canned Beets -- diced or sliced (pint jar or 15 Â½ oz can) 2 tablespoons Cornstarch -- or cook-type clear jel Â¼ cup Sugar Â½ teaspoon Salt 1 cup Beet Liquid -- or water as needed to make amount 1/4 cup Vinegar 1 tablespoon Butter Mix cornstarch, sugar and salt.