In a large bowl, season the short ribs with onion, green onion, garlic, ginger, thyme leaves, Scotch bonnet (if chopped), olive oil, browning, soy sauce, brown sugar, salt, and pepper. Cover and allow to marinate in the fridge overnight, or at least a few hours.
Heat vegetable oil in a large Dutch oven over medium-high heat. Sear the seasoned short ribs (shaking off the excess marinade) on all sides until browned, about 4-5 minutes per side. Once done, remove the ribs from the pot and set them aside.
Add the marinated onion, green onion, garlic, ginger, thyme, and remaining seasonings from the bowl to the pot. Cook for about 3-4 minutes, stirring occasionally, until softened and fragrant.
Pour in the beef broth and water, scraping up any browned bits from the bottom of the pot. Bring to a gentle simmer then add the bay leaves and whole pimento berries. Return the seared short ribs to the Dutch oven, ensuring they’re fully submerged in the liquid.
Cover and transfer to the preheated oven at 325°F (160°C). Let the short ribs braise for 2.5 to 3 hours, or until the meat is tender and falling off the bone. As the short ribs cook, you may need to reseason with fresh herbs or additional seasonings towards the end to keep the flavours balanced and vibrant.
About 20–30 minutes before the short ribs are done braising, stir in the sliced red and green bell peppers. This gives them time to soften while still keeping a bit of texture and vibrant colour.
Carefully remove the short ribs from the Dutch oven, discard the bay leaves, thyme sprigs, and pimento seeds, and return the pot to the stove over medium-high heat.
Simmer the braising liquid, stirring occasionally, until it reduces by about half and thickens into a rich sauce. Taste test and adjust the seasoning with salt, pepper, or fresh herbs as needed.