Process all ingredients for the chilli paste with the exception of the green chillies in a mortar or mixer to a fine paste. Mix in the green chillies.
Heat 200ml coconut milk in a saucepan. Add chili paste and cook for 2 minutes. Add the beef sirloin and the rest of the coconut milk and bring the pot contents to a boil. Add the fish sauce and palm sugar, cook for another 2 minutes, then add the aubergines and red chillies and cook for 1 minute. Stir in the torn lime leaf and cook for 1 minute, then add the basil and remove the pan from the hob.
Serve the curry in bowls with rice. Pork or chicken can also be used instead of beef.