Melt butter in a pan. Add the onion, lemongrass, garlic and green chili. Saute till they turn slightly brown in colour.
Add the stock cube, water, coconut milk, salt, pepper powder, coriander leaves and kaffir lime leaves. Pressure cook for 3-4 whistles.
When it cools down, discard the lime leaves and blend until smooth. Add lime juice and strain through a sieve.
Garnish with coriander leaves & red chili flakes. Serve at room temperature or chilled, accompanied with soup sticks or croutons.
