In large frying pan, saute onion and celery in olive oil about 5 minutes, until starting to soften. Add garlic and cook about 2 minutes more.Then add ham and saute over very low heat 10 minutes. (Don’t skip this step, which concentrates the ham flavor into the vegetables.)Transfer mixture to large soup pot, add chicken stock, black eyed peas, dried thyme, and ham rinds if available, and cook at very low simmer for one hour.After soup has cooked one hour, taste for flavoring. Add more water and ham flavor base if needed. (It will depend on your ham, but I usually add a tiny bit. I added about 2 cups more water to the soup at this point.)Add chopped collard greens, stir into soup and simmer one hour more, or until black-eyed peas are quite soft.When black-eyed peas are as soft as you want them, remove pieces of ham rind, then use an immersion blender, food processor, or hand masher to partially process about half the soup. You want a mixture of broken and unbroken black-eyes peas, with some thickening of the soup from the pureeing process. Be careful not to over process.Add red pepper flakes and vinegar and simmer 10 minutes more (or longer, I sometimes cook as much as an hour more at this point.)Serve hot.