1 lbs cooked beetroot (not pickled), roughly chopped; 1/2 quart tin light coconut milk; 2 tbsp Thai fish sauce; Juice of 1-2 limes; ½ tsp salt; 4 shallots, finely chopped; 3 garlic cloves, finely sliced; 4 stalks lemongrass, trimmed and chopped; 2 x 3cm pieces galangal, finely sliced; 2 thumb-size pieces of root ginger, grated; 6 makrut lime leaves, shredded; 1 tbsp vegetable oil; 3 cups cold water; 2 ounces coriander, stalks and leaves chopped (reserve a few leaves for garnishing); 1 bird’s-eye chilli, deseeded and finely sliced
(1) In a large MEC pot, fry the shallots, garlic, lemongrass, galangal, root ginger and makrut lime leaves in vegetable oil for 5-6 minutes to release their flavor.
(2) Add the water and the rest of the stock ingredients. For more heat, add a few chili seeds to the pan. Bring to the boil, then simmer for 40 minutes before straining and discarding the solids.
(3) Put the stock back into the pot, add the chopped beetroot and bring back to a simmer for 10-15 minutes. Blitz with a stick blender, then add the coconut milk and bring the pot back to a simmer again.
(4) Add fish sauce, salt and lime juice to taste: the soup should taste sharp and sweet. Serve with the reserved whole coriander leaves.