In a small frying pan, separately roast the hop bap, star anise, cassia bark and cloves until fragrant and slightly coloured, then grind them in a mortar. Combine the spices and the remaining marinade ingredients in a large bowl, add the beef brisket and mix well. Refrigerate and marinate overnight.
Place a wok over medium heat and add the oil, diced onion and garlic.
Stir-fry until the onion becomes translucent, then add the beef brisket and increase the heat. Continue to fry until the meat is sealed on all sides. Add the tomato paste and combine it with the beef and stir-fry for 1 minute. Add the pho stock and salt and bring it all to the boil. Skim the impurities from the surface, then lower the heat to a slow simmer. Cook the beef for about 2 hours, or until it is very tender.
Once cooked, add the carrots and cook for a further 5 minutes. To serve, divide between 6 bowls and garnish with sliced onion rings and Vietnamese basil.