1. Steam Lobster: In a large pot lined with a steamer basket, bring 1 inch of water to a boil. Drop the lobsters headfirst into the pot and cover. Reduce heat to a simmer and steam until the shells just turn bright red, 12 to 14 minutes. To check for doneness, pull on an antenna; if it releases from the shell with little resistance, the lobster is properly cooked. (Many seafood markets will do the steaming for you -- just ask.)

2. Extract Meat: Hold the tail in one hand and the body in the other; twist and pull to separate. For claws and legs, twist and pull where they're attached to the body. Use lobster- or nutcrackers or a mallet to crack the shells. To get all the meat out in one swift motion, insert a fork into the underside of the tail and push up. Then chop into bite-size pieces.

3. Mix, Toast, and Fill: In a bowl, stir together mayonnaise, lemon juice, and salt. Fold in chopped lobster meat. Heat a large skillet (preferably cast-iron) over medium. Generously brush top and sides of buns with butter. (Top-split are narrower than side-split, so you get a greater ratio of lobster to bread.) Place buns, flat-side down, in skillet and toast, flipping halfway through, until crisp and golden on both sides, about 3 minutes. Divide lobster meat among buns and serve, with lemon wedges and potato chips.