Step 1: Thoroughly clean the collard greens. Fill a large sink or basin with cold water. Submerge the collards, swishing them around to loosen any dirt. Drain and repeat this process 2-3 times until no grit remains at the bottom of the sink.
Step 2: Remove the tough stems. Fold each leaf lengthwise and cut or tear away the thick central rib. You want mostly the tender leaf portion for cooking.
Step 3: Stack 5-6 leaves on top of each other, roll them tightly like a cigar, and then slice them crosswise into 1-inch ribbons.
Step 4: In a large Dutch oven or heavy-bottomed pot, add the smoked ham hocks and cover with about 8-10 cups of cold water or chicken broth. Bring to a boil, then reduce heat to low, cover, and simmer for 1 to 1.5 hours, or until the meat is tender and easily pulls from the bone.
Step 5: Carefully remove the ham hocks from the pot liquor, setting them aside to cool. Once cool enough to handle, pull the meat from the bones, shred it, and set aside. Skim any excess fat from the pot liquor if desired, but leave some for flavor.
Step 6: In the same pot with the pot liquor, add a tablespoon of olive oil or bacon grease. Sauté the chopped onion until softened and translucent, about 5-7 minutes.
Step 7: Add the minced garlic and cook for another minute until fragrant, being careful not to burn it.
Step 8: Begin adding the sliced collard greens to the pot in batches. Stir each batch until slightly wilted before adding more.
Step 9: Once all the greens are in the pot, stir in the red pepper flakes (if using) and season with salt and black pepper to taste. Remember, the ham hocks add saltiness, so taste before adding too much.
Step 10: Return the shredded ham hock meat to the pot. Bring the liquid to a gentle simmer, then reduce the heat to low, cover the pot, and cook for at least 1 to 1.5 hours, or until the greens are very tender. Stir occasionally and add more water or broth if the pot liquor reduces too much.
Step 11: Once the greens are tender, remove the pot from the heat. Stir in the apple cider vinegar. This brightens the flavor and balances the richness.
Step 12: Taste and adjust seasonings one last time. You might need a little more salt, pepper, or a touch more vinegar to get them just right.
Step 13: Serve hot, with plenty of that incredible pot liquor.