Put all the ingredients except 100 ml (3½ fl oz) of the oil and the lime leaves into the bowl of a food processer and whizz until it forms a smooth paste. Heat the remaining oil in a heavy-based saucepan over a high heat, add the paste and immediately reduce the heat to medium. Add the lime leaves, stirring constantly as the paste may catch on the bottom of the pan. Cook for about 15 minutes, or until the oil starts to separate from the paste. Taste the paste: it is cooked when it no longer tastes of raw garlic or onion.
Put the beef short ribs in a heavy stockpot and cover them with cold water. Bring to the boil over a high heat then drain as soon as it reaches boiling point, discarding the water. Give the ribs a good wash to remove any bits of scum or impurities, and wash out the pot. Return the ribs to the pot, add the remaining ingredients and 500 ml (17 fl oz/2 cups) water. Give everything a stir and bring to the boil. Once the pot reaches boiling point, reduce the heat to low and simmer for 3 hours, or until the beef is tender and almost falling off the bone.
Combine the herbs in a small bowl and dress them with nuoc cham when ready to serve. Present the curry with the herb salad on the side and, ideally, a fresh Vietnamese baguette.