The best way to prepare a whole frozen lobster is to allow the lobster to thaw first, but it is possible to cook the lobster while it is frozen. Boiling is the method to prepare a whole frozen lobster.
Boil 3 quarts of water per lobster in a large pot. Salt the water with 6 tablespoons of salt per lobster. Multiple lobsters can be cooked at the same time, but their cook time varies by weight so keep that in mind if the lobsters are of different sizes.
Add the frozen lobster once the water is boiling, making sure that it continues to boil after the lobsters were added, then cover the pot and remove it from the heat. The weight of the lobster determines how long to leave it in the hot water. Allow nine minutes for 1-pound lobsters, 11 minutes for 1 1/2-pound lobsters, and about fourteen minutes for two pound lobsters.
To test that the lobster is fully cooked, use tongs to remove it from the water. Then, insert a meat thermometer through a gap between the body and the tail into the thickest part of the tail. The lobster needs to reach 160 degrees Fahrenheit to be safe to eat.