For a cleaner flavor, place them in a pot, cover with water, bring to a boil for 5 minutes, then drain and rinse.
3
Put the feet in a clean pot with 2.5 liters of fresh water and the vinegar.
4
Bring just to a boil, then lower the heat and simmer gently, partially covered, for 5–6 hours; skim any foam from the surface and add a little hot water if needed to keep the feet covered.
5
Strain the liquid through a fine sieve, discarding the solids.
6
Pour the liquid into a clean pot and simmer until reduced to about 500 ml (2 cups).
7
Transfer to a shallow container and cool briefly, then refrigerate promptly until fully set, about 8 hours.
8
Skim off any solidified fat.
9
The firm, unseasoned gel is homemade gelatin; keep refrigerated and use within 4 days, or freeze.