Nam tok is a Thai dressing often used on grilled meats or fried fish; it's simple to make and pairs well with lobster, too. It's refreshing, zingy, and spicy. Serve with jasmine rice.
Bring a large pot of water to boil over high heat. Dispatch the lobster using a chef's knife, and break apart the body, but do not boil the lobster. Reserve the head for making stock, or discard.
Flip the tail over so that the legs are facing up, and insert a butter knife into the tail, wedging it in between the shell and the meat. (This will keep it from curling up like a shrimp when cooking, and will make it easier to remove the meat when cooked.) Drop the tail into the water, and cook until the shell is bright red; do not overcook. (For a 1 ½-pound lobster, it will take about 5 minutes for the tail.) Remove from the pot with a pair of tongs and drain in a colander set over a bowl.
Next, cook the claws. For a 1 ½-pound lobster, this will take about 7 minutes. (A general rule of thumb is to cook the claws just 2 minutes longer than the tail.) Remove from the pot with a pair of tongs and drain in the same colander as before.
To make the dressing, combine the onion, half of the scallions, habanero, lime juice, and fish sauce in a bowl. Add the toasted rice powder and cilantro, if using.
Remove the butter knife from the tail (use oven mitts because it will be very hot), and carefully use kitchen shears to cut through the shell. Working over a bowl to reserve the juices, remove the meat from the shell. Next, carefully use the heel of a chef's knife and kitchen shears to crack through the claws or lobster crackers if you have them. Working over a bowl, remove the meat. Slice the tail meat into approximately ¼-inch rounds. Pour any reserved juices into the dressing. Arrange the lobster on a plate, and top with the dressing. Garnish with the remaining scallions, and serve with jasmine rice.