Heat the olive oil in a large pot over medium heat. Place the oxtail in the pot, searing on each side for 2-3 minutes each, until all sides are browned. Use tongs to remove the oxtail and set aside on a plate for now, leaving any drippings in the pot.
Add the onion, carrots, and habanero. Reduce heat to medium-low and cook for 5 minutes, until the vegetables start to get tender.
Add the garlic, brown sugar, Worcestershire, cinnamon, cloves, and pepper. Cook for one minute, stirring well.
Add the tomato paste and diced tomatoes, giving everything a good stir. Return the oxtail to the pot, and add the beef broth.
Bring to a boil, then reduce heat to low and simmer, covered, for 2 hours and 15 minutes. Remove the cover and continue simmering another 1 hour, until the liquid has reduced by at least half forming a lovely stew-like consistency. (If necessary or desired, let cool then skim any fat off the top*.)
When the oxtail is nearing completion, prepare the grits.* Combine the water, milk, and salt in a medium-sized pot and bring to a simmer over medium-low heat. Stir in the grits, mixing well so they do not clump. Cover and continue cooking, stirring occasionally, approximately 5-7 minutes total for quick grits (or 15-20 minutes for regular grits), until the grits are creamy. Turn off the heat and stir in the butter until fully melted and mixed in.
Serve the braised oxtail with some of the stew over the grits. Garnish with scallions. Enjoy!