Meanwhile, peel onion. Cut in half through the root and slice thinly. Peel carrots and cut them lengthwise in half, then cut the halves crosswise into 2 inch pieces.
Heat a wok or a large pot over high heat. Drizzle 2 T oil and continue heating until the oil is hot. Add half of the marinated beef and stir-fry until browned on all sides, about 5-7 minutes. Transfer to plate. Add another 2 T of oil and cook the rest of the meat.
Transfer the beef and juices to a plate. Reheat wok or pot and add the onion and stir-fry for a minute. Return all the beef and its juices to the wok. Add star anise, tomato paste, stock and the chili. Stir well to mix. Bring to a boil, cover and simmer over low heat, about 1 1/2 - 2 hours, stirring occasionally.
Season with sea salt. Add the carrots and continue cooking until the beef and carrots are tender.
The stew should be rich, but not too thick. Season to taste.
Remove the chili (or remove them when you have reached the desired heat) and the star anise.
Add torn basil leaves and cilantro leaves. Mix well. Serve hot with steamed rice, rice noodles or baguette.