1 1/2 pounds (680g) meaty smoked ham hocks (see note)
2 medium yellow onions (about 1 pound; 450g), sliced into 2-inch lengths
4 medium cloves garlic, crushed
2 quarts (1.9L) homemadechicken stock, low-sodium store-bought chicken broth, or water
3 pounds (1.3kg) collard greens, woody stems trimmed and leaves cut into thick ribbons
Kosher salt and freshly ground black pepper
Apple cider vinegar, to taste (optional)
In a large pot or Dutch oven, combine ham hocks, onions, garlic, and chicken stock and bring to a simmer. Cover and cook at a bare simmer until hocks are very tender, 2 to 3 hours.
Remove ham hocks from liquid, transfer to a cutting board, and pull bones from meaty and fatty parts. Discard bones. Chop up meat into chunks and return it to pot.
Add collard greens, pressing down to submerge in liquid. Return to a simmer and cook, uncovered, until collards are very tender, about 30 minutes. Season with salt and pepper. Add vinegar to taste, if desired, then serve. (You can add vinegar to the pot, or let individual diners season their greens with it at the table.)