Toss the pork with vinegar, garlic, ginger, allspice, scallion whites, salt, and pepper. Cover and marinate in the fridge for at least 30 minutes, or overnight.
Heat the oil in a Dutch oven over medium heat. Add the brown sugar and stir constantly until it melts into a deep amber color, about 2–3 minutes. Watch closely — it can burn quickly.
Immediately stir in the browning sauce, then add the marinated pork in batches. Sear for 3–4 minutes per side until deeply browned. Remove and set aside.
In the same pot, add the sliced onion and cook 2–3 minutes until softened, scraping up any browned bits. Stir in the remaining thyme, ketchup, and soy sauce.
Return the pork to the pot. Add the chicken stock, bouillon cube, and scotch bonnet pepper. Bring to a boil, then reduce to a low simmer and cover.
Simmer for 1.5 to 2 hours, checking occasionally, until the pork shreds easily with a fork and the gravy has thickened.
Stir in the carrots, bell peppers, and scallion greens. Simmer uncovered for 15–20 minutes more, until the vegetables are tender and the gravy coats the back of a spoon.
Taste and adjust salt. Remove the scotch bonnet before serving unless you want extra heat left in the dish.