Fill a very large (18- to 20-quart) stockpot 3/4 full with water, add 2 tablespoons of salt, cover and bring to a full rolling boil. Immerse the lobsters in the water and cook for 10 minutes, until an instant-read thermometer inserted into the middle of the underside of a tail registers 140 degrees F. (Don't worry if the water doesn't come back to a boil.) Remove the lobsters with tongs and set aside until cool enough to handle. Remove the lobster meat from the shell, including the claws.
Ina asks the seafood shop to kill the lobsters for her, but they must be cooked very soon afterward. To do it at home, place the tip of a large chef's knife exactly where the head and tail connect and plunge it quickly into the lobster. You'll sever the spinal cord and the lobster won't suffer.