01 - Heat olive oil or bacon drippings in a large pot over medium heat. Add diced onion and cook for 4 to 5 minutes until translucent.
02 - Stir in minced garlic and cook for 1 additional minute until fragrant.
03 - Add smoked turkey leg or ham hock if using, then pour in chicken broth. Bring to a simmer.
04 - Add the chopped collard greens in batches, stirring each time until wilted and all the greens fit comfortably in the pot.
05 - Stir in salt, black pepper, and red pepper flakes if using. Reduce heat to low, cover, and let simmer for 1 hour, stirring occasionally, until greens are tender.
06 - Remove meat bones. Shred any remaining meat and return it to the pot. Stir in apple cider vinegar.
07 - Taste and adjust seasoning as needed. Serve warm.