Vietnamese Spicy Beef Noodle Soup

Soak 500 g beef shank in cold water for 1 hour, changing the water if it becomes very red.

Bruise the thick root ends of 3 lemongrass stalks so their aroma can infuse the broth.

Put the drained beef, bruised lemongrass, and 2 L water in a pot, then bring it to a boil over high heat.

Skim off foam as it rises so the broth stays clean and not muddy.

Once boiling, lower to a gentle simmer and cook for 1 hour 30 minutes to 2 hours.

The beef is ready when a chopstick or skewer slides in with little resistance, then lift it out.

Stir in 1 tbsp shrimp paste, 2 tbsp fish sauce, 1 tsp sugar, and 3 dried chilies, then simmer for 10 minutes.

If using fully cooked blood sausage, heat it in the broth for the final 5 minutes and remove it before slicing.

Cook 400 g round rice vermicelli until tender but springy, then rinse under cold water.

Divide into bowls and top with thin beef slices and the blood sausage heated in the broth, if using.

Bring the broth back to a hot simmer before ladling it generously over the noodles and meat.

Serve bean sprouts, optional banana flower, and lime alongside so their crunch and acidity cut through the rich broth.