Heat vegetable oil in a heavy stewpot over a high flame until hot (but not smoking). Season oxtails with salt and pepper. Working in batches, brown the oxtails. Return all meat to pot and add wine. Cook uncovered over medium heat until liquid is reduced to a thick syrup, about 20 minutes. Add broth and bay leaves. Stir to deglaze, scraping browned bits up from bottom of pot with a wooden spoon. Cook uncovered at a fast simmer for 1 hour. Add yucca and fresh potatoes (if used) and continue cooking about 45 minutes more until meat, yucca and potatoes are tender. If using the papas coriollas, add them now along with half the cilantro, cooking another 5 to 7 minutes until heated through. Salt and pepper to taste. Serve immediately, sprinkled with remaining cilantro and 1 tablespoon sofrito per serving.
For Sofrito: Heat oil in saucepan over medium heat. Add remaining ingredients and cook for about 7 minutes.