put meat, vegetables, salt and whole garlic cloves in a big pot. If your foot is frozen you can put it in frozen. Its imporatnt to use feet or knees, "soup bones" wont cut it!
add 5c water. This step is not as important as you can always add more or boil it down.
put black pepper in a cheesecloth or tea bag. Makes it easier to remove when done cooking.
Simmer 1-2 hours until meat is tender. I prefer to use veal meat as its more tender but beef will do. You can even cut up a cheap cut of steak or roast.
Skim off any fat of foam that may form.
Discard the vegetables.
Now is the fun part. You get to butcher the foot. It should be falling apart, if its not you need to boil it longer. Take it out and put it in a bowl. Theres a thick skin and some fat on the outside of the foot, throw that away. Throw away any toes or bones which may have fallen off. You want to KEEP any tendons or cartelege you can get off. There should be a large tendon running along the back of the foot, as well as lots of (edible) cartiledge connecting all the bones together. The tendons are good to eat, but if its not your cup of tea you dont need to keep the cartiledge.
Chop the foot "meat" into bite size pieces (1/4"), and put it back into the pot and boil for 15 more minutes, skimming any more fat or foam.
Take out the cheesecloth of black pepper. You can discard some but throw some pepper back into the pot, its a nice surprise to bite into a piece of pepper when eatiing this.
Tast the liquid. It should be strong, if not add more salt. This will be served cold, and stuff tastes more bland when cold.
The important part is how much gelatin you got out of the foot bones. With 1 cow foot (hock attached) you should be left with 4 cups of cooked liquid afterwards.
Pour into a deep 9x13" pyrex dish. The liquid should come up about 1". Put it in to the fridge to set 8 hours. If you press on it with your finger it should give a lot of resistance. Not to make this sound any less appetizing than it is, but you'll end up with a white, or slightly brown brick of meat!
If you did not get the desired consistency, dont fret! Scrape off any fat which you didnt get by skimming, throw the slightly set jelly back into a pot and boil it down for another 30 minutes, and reset.