Cut the carrots into chunks. Bruise the lemongrass stalks.

Heat a pot with 2 tablespoons cooking oil. Sauté chopped shallots until fragrant, then add the beef and stir-fry until browned. Add the lemongrass.

Pour about 4 cups water (1 liter) into the pot with the beef. Add the carrots and simmer until the beef is tender. Mix 1 tablespoon tapioca starch with a little water, then slowly add to the stew to slightly thicken. Taste and adjust seasoning as needed, then add the onion.

Blanch the bean sprouts and hu tieu noodles, then place them in bowls. Ladle the beef stew over the noodles and serve with fresh herbs and culantro.