Step 1

Spray a large, heavy-based saucepan with oil. Heat over medium-low heat. Add onion. Cook, stirring, for 5 minutes or until softened. Add ginger and curry paste. Cook, stirring, for 1 minute or until fragrant.

Step 2

Add sweet potato, lentils, stock and 2 cups cold water. Bring to the boil. Reduce heat to low. Simmer, partially covered, for 15 to 20 minutes or until potato and lentils are soft. Set aside for 5 minutes to cool. Process until smooth.

Step 3

Return mixture to pan over low heat. Add lime juice, fish sauce and sugar. Cook, stirring, for 5 minutes or until heated through. Serve topped with coriander.