Heat 2 tbsp of olive oil in a large pot on medium heat. Clean and season oxtails with salt and pepper, place in the pot and cook until all the sides are browned. Take them out of the pot, place them on a plate and set aside.
Place the diced onion into the pot and cook until translucent but not browned. Add chopped garlic and chillies into the pot. Cook for 1 minute. Stir in smoked paprika, soya sauce and tomato puree. Cook for 2-3 minutes.
Place the oxtails back into the pot. Pour the beef stock, add bay leaves, and bring the stock to boil. You want the oxtails to be just covered in the stock so add more if needed. Cover the pot with the lid, leaving a small crack, and cook on low-medium heat for 4 hours. Check the stew from time to time to add more water if needed.
Serve with rice and a sprinkle of chopped spring onion.