1.5 kg (3 lb) beef shank and pork knuckle or hock, 1 kg (2 lb) pork or beef bones
6 stalks lemongrass, bruised and tied, plus 2 stalks finely minced
1 onion halved, 1 tbsp fermented shrimp paste (mắm ruốc) loosened in 125 ml (1/2 cup) water
To season: 3 tbsp fish sauce, 1 tbsp sugar, 2 tsp salt
For the chili oil: 4 tbsp neutral oil, 2 shallots and 4 cloves garlic minced, the 2 minced lemongrass stalks, 2 tbsp chili flakes, 1 tsp annatto seeds or paprika
800 g (1 3/4 lb) thick round rice noodles (bún bò), cooked as the pack says
To serve: shredded banana blossom or cabbage, bean sprouts, mint, Thai basil, lime, sliced onion and scallions
How to make it
Blanch (15 min): Boil the meat and bones 10 minutes, drain, rinse.
Simmer (2 1/2 hr): Cover with 4 liters (4 quarts) fresh water, add the lemongrass bundle and onion, simmer gently, skimming. Lift out the shank when tender (about 1 1/2 hours) and the hock at 2 1/2. Let the shrimp paste water settle and pour only the clear top into the broth. Season with fish sauce, sugar and salt.
Chili oil (10 min): Fry the shallots, garlic and minced lemongrass in the oil on low until golden, add annatto or paprika and chili flakes off the heat. Stir half into the broth; keep the rest for the table.
Build (5 min): Put noodles in big bowls, top with sliced shank and pieces of hock, ladle over very hot broth, and finish with onion and scallions. Herbs, sprouts and lime on the side.
Tips
Shrimp paste is strong; add it a spoon at a time and taste.
Huế cooks add cubes of pork blood and crab cakes; add them if you can find them.