Lobster can be cooked like crab, in boiling water. For a quicker, more humane method, stab the head just behind the eyes, bringing the knife through to the cutting board, then pressing it forward to divide the head.
To prepare for boiling, kill the lobster and split it lengthwise. Remove the stomach sac and pull out the intestinal vein. Scoop out the tomalley and roe, and rinse under cold water. To prepare frozen lobster tail, defrost, then cut the inner edges of the under-shell with a pair of scissors. Clip off the fins, pull back the shell and discard. Bend the tail back to crack the joints. Rinse with cold water.
Fill a large pan with at least 1 gallon (3.79 liters) of water plus another quart for each additional lobster and bring to a rapid boil. One at a time, plunge live or prepared lobsters headfirst into boiling water. Reduce heat and simmer five minutes for a 1 1/4 pound (about 567g) lobster plus two minutes for each additional pound (about 454g).
Place whole, cooked lobster (or lobster tail) meat-side-up in a broiler pan. Brush with lemon and oil or melted butter. Place 4 inches (10cm) from heating element or flame and broil until meat is heated through. Follow the same method to cook raw lobster tails, except broil tail-side-up for four minutes, then turn, brush with butter or oil, and broil until meat is opaque (four to five minutes).
Kill the lobster, split it lengthwise, and remove the sand-colored grain sac from each side of its head. Twist off claws. Heat oven to 400°F (200° C). Place claws on a shallow baking pan and cook about eight minutes. Remove pan from the oven, then add lobster halves flesh side up. Brush with lemon juice and oil or melted butter and cook for an additional ten minutes.
Place an inch or two (about 2.5 to 5cm) of water in a large pot and bring to a boil. Put the whole, live lobsters (or kill them first by splitting the head) in the pot and steam for about five minutes. Use the cooking liquid as base for a sauce.
Soups or stews
Boil lobster lightly—the meat should not be fully cooked. When cool, crack shells and remove meat, tomalley, and coral. Break up shells with a hammer and boil them in water to form a savory broth. Strain the broth to remove shells, then add herbs, spices, and vegetables. Add lobster meat during the final few minutes of cooking.