Canh Khoai Mỡ

the purple yam soup of the Mekong delta: grated khoai mỡ melting into a clear prawn or pork broth until it turns thick and violet, finished with rice paddy herb

Origin: The Mekong Delta & Southern Vietnam

From the journey of Yam.

Khoai mỡ is the purple water yam, Dioscorea alata, and southern Vietnam cooks it into one of its most everyday soups. The yam is scraped from its skin rather than chopped, in short strokes that leave it in soft shreds, and dropped into a light broth of prawns or minced pork, where it dissolves and thickens the soup to a violet cream while a few pieces stay whole. It is finished with ngò om, rice paddy herb, whose lemony scent is the flavour southerners associate with the dish, and with fried shallots and black pepper. It is family cooking rather than restaurant cooking, eaten as part of a rice meal beside a salty fried fish, and it belongs to the delta, where the yam grows easily. Mainland Southeast Asia is one of the places where botanists now read a separate domestication of the greater yam, alongside the Pacific.

Ingredients

Soup

  • 600 g purple yam (khoai mỡ)
  • 200 g raw prawns, peeled and roughly chopped, or minced pork
  • 2 shallots, finely chopped
  • 1 tbsp vegetable oil
  • 1.5 litres water or light stock
  • 2 tbsp fish sauce
  • 1 tsp sugar
  • Salt and black pepper

To Finish

  • 1 small bunch rice paddy herb (ngò om), chopped
  • 2 spring onions, sliced
  • 2 tbsp fried shallots

Method

  1. Halve the yam and scrape the flesh out of the skin with a spoon or the edge of a knife in short strokes, so that it comes away in soft shreds.
  2. Heat the oil and fry the shallots until fragrant, then add the prawns or pork and stir until they change colour.
  3. Pour in the water, bring to the boil, and skim.
  4. Add the yam a spoonful at a time, stirring after each, and simmer for 12 to 15 minutes until the soup has thickened and turned violet.
  5. Season with fish sauce, sugar, salt, and pepper.
  6. Take off the heat, stir in the rice paddy herb and spring onions, scatter with fried shallots, and serve with rice.

Notes

Rice paddy herb is sold fresh or frozen in Vietnamese grocers and has no real substitute; coriander changes the dish but keeps it good. The soup thickens as it stands; loosen with hot water when reheating.

The Gastrographer

The Gastrographer

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Became a culinary stapleColonial / trade control
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