Twist off the claws from the lobsters, crack them open and remove all the meat. Remove the meat from the body, then cut all the meat into 1cm (1/2-inch) cubes, reserving the trimmings and the shells.
To make the stock, put all the ingredients in a large pan and bring to the boil. Reduce the heat and simmer for 20 minutes, then strain through a fine sieve and set aside. To make the spice mix, pound all the ingredients together to a coarse paste in a mortar and pestle.
Heat the oil and half the butter in a saucepan, add the spice mix and curry leaves and sauté until the garlic turns golden brown. Add the chilli powder and the lobster trimmings and sauté for a minute. Add the tomatoes and salt and stir till the tomatoes soften.
Now add the stock and bring to a simmer. Reduce the heat and cook gently for 30 minutes. Remove from the heat and leave to cool. Blend the soup with a hand blender and pass it through a fine sieve.
Heat the remaining butter in a large saucepan, add the lobster meat and sauté for a minute.
Pour the soup into the pan and bring to a simmer. Stir in the coconut milk, cream, sugar, lemon juice and coriander, then remove from the heat.
Pour the brandy into a ladle and warm it over a low flame until it catches fire. Pour the brandy over the soup, cover and leave to stand for 2 minutes.
Divide the soup and lobster meat between 4 soup plates and serve straight away.
