Add enough water to a large pot to reach a depth of 2 to 3 inches. Bring it to a rolling boil. Place a colander or a wire cooling rack over a rimmed baking dish.
Carefully remove the rubber bands from the lobster claws. Lower the lobsters into the boiling water, shell side down, cover the pot, and cook until done, about 11 minutes.
Using tongs, remove the lobster from the boiling water and transfer them to the colander or the rack to drain and cool to room temperature.
When the lobster is cool enough to handle, use your hands to separate the lobster tail from the body. Using a fork, remove the tail meat.
Using a cracker, the flat side of a chef's knife, or the bottom of a heavy skillet, crack the claws and legs and remove the meat. The red roe, or coral, found in female lobsters, is considered by many to be a delicacy and can be reserved for another use. Coarsely chop the lobster tail and claw meat. Reserve the shells for making stock or discard.
In a bowl, mix the mayonnaise (using a little more or less, depending on how creamy you like it), lemon juice and zest, chives, scallion, just a touch of salt, and pepper to taste.
Gently fold the lobster meat into the mayonnaise mixture. Taste and adjust the seasoning accordingly. Cover and refrigerate for no more than 3 to 4 hours.
In a skillet over low heat, melt the butter. Cut the baguette pieces in half lengthwise and place them, cut side down, in the puddle of butter. Toast the baguette until it just begins to turn golden brown. (Alternately, brown the hot dog rolls until they begin to turn golden brown, flipping them over so they get toasted and buttery on both sides.)
Divide the lobster between the pieces of toasted baguette. Serve (and devour) immediately.