Trim any excess fat from the oxtail and pat dry with paper towels.
In a large bowl, combine the oxtail with browning sauce, soy sauce, Maggi seasoning, Worcestershire sauce, allspice, all-purpose seasoning, garlic powder, onion powder, black pepper, minced garlic, chopped onion, and chopped Scotch bonnet peppers.
Mix thoroughly until every piece of oxtail is evenly coated in the marinade.
Cover and refrigerate for at least 2–3 hours, preferably overnight, to allow the flavors to develop.
Heat a generous amount of vegetable oil in a large Dutch oven or heavy-bottomed pot over medium heat.
Add the brown sugar and allow it to melt and darken into a deep amber color. Watch carefully to prevent it from burning.
Carefully add the marinated oxtail in batches, reserving the marinade. Brown each side for a few minutes until nicely caramelized. Avoid overcrowding the pot.
Remove the browned oxtail and set aside.
Add the reserved marinade to the pot and cook for 2–3 minutes, stirring to release the browned bits from the bottom.
Pour 4 cups of water or beef broth into the bowl used for marinating to collect any remaining seasoning. Add it to the pot.
Return the browned oxtail to the pot. Add bay leaves, ketchup, and the whole Scotch bonnet pepper, if using.
Add the carrots, cover, and simmer over low heat for approximately 2½–3 hours, or until the oxtail is fork-tender.
Add the rice to a rice cooker and rinse under cold water until the water runs mostly clear. Drain well.
Add the coconut milk, water, kidney beans, garlic, allspice, and salt.
Stir gently to combine, close the lid, and cook using the regular white rice setting.
Once the rice cooker finishes, let the rice rest for 10 minutes before fluffing with a fork.
Once the oxtail is tender, add the drained butter beans and gently stir.
Simmer for another 20–30 minutes to allow the beans to heat through and absorb the gravy.
Stir the cornstarch slurry and slowly add it to the pot to thicken the gravy. Simmer for a few more minutes until the sauce reaches your desired consistency.
Remove the bay leaves and whole Scotch bonnet pepper.
Serve the oxtail hot over Jamaican rice and peas with plenty of gravy. Enjoy!