Clean feet carefully and cover with hot water. Simmer until meat will separate from bones, then remove carefully with skimmer. Place in stone jar, taking out the largest bones. Save the water for later use and let cool. Heat vinegar with bay leaves, cloves, cinnamon, salt, pepper, onion, and mace. Simmer slowly for 45 minutes but do not boil at any time. Remove cake of fat from top of saved cooking water. Add about 1 quart of the water to vinegar; if vinegar is not very strong, use less water. Strain liquid through a sieve and pour over meat in jar. Chill 2 days.