Place lobster tails shell-side up with the tail end away from you. Cut through the top of the shell Snipping through the shell and top portion of the meat as you go. Stop at the base of the tail.
Flip the tail over to the see-through side and crack the ribs using both thumbs down the center. This helps open the shell. Remove and discard the vein if you see one.
Carefully run your thumbs down the sides of the meat to loosen it from the shell (CAREFUL! Those shells can be sharp!). Lift the meat from the shell, keeping it attached at the base then press the shell together underneath and set the lobster meat back over the top, opening up the meat to butterfly the tails. Butterfly remaining tails and transfer to a casserole dish.
Broiled Lobster Tails:
Preheat oven to Broil on high heat with rack in the center of the oven. Place the rack so the top meaty portion of the lobster tails is about 6" away from the top heating element.
In a small mixing bowl, combine the marinade ingredients: 1 Tbsp parsley, 2 pressed garlic cloves, 1 tsp dijon mustard, 1/4 tsp salt, pinch black pepper, 1 1/2 Tbsp lemon juice and 1 1/2 Tbsp olive oil. Stir to combine then spoon it all over the lobster tails. Dot the top of lobster tails with 2 Tbsp of butter.
Arrange lobsters in a rimmed oven-safe casserole and place under the preheated oven broiler to broil 10-11 minutes or according to the lobster tail size chart below. The finished lobster should be white and opaque in the center and register at least 145˚F on an instant read thermometer.
Lobster Dipping Sauce:
As soon as lobster tails come out of the oven, transfer to a serving platter. Pour drippings from the pan into a small saucepan over medium heat. Melt in 2 Tbsp butter and remove from heat just as soon as the mixture starts simmering. Spoon the lobster butter sauce over the tails and serve. You can also serve the sauce in ramekins on the side for dipping.
Broiling Times for Lobster Tails:
Smaller (3 to 4 oz) lobster tail 6 to 8 min
Medium (5 to 6 oz) lobster tail 10-11 min
Larger (7 to 9 oz) lobsters tail 12-15 min (with rack in middle of oven)
Broil lobster meat until opaque and white in center, or 145˚F.