Prepare Lobster Tails: Begin by using kitchen scissors to cut through the top shell of each lobster tail, stopping at the base without cutting the meat. Gently crack the ribs and open up the shell to butterfly the tail, lifting the meat slightly so it sits on the shell.

Preheat Oven: Set your oven rack in the upper third position and preheat it to high broil.

Make Marinade: In a mixing bowl, combine chopped parsley, minced garlic, Dijon mustard, fine sea salt, freshly cracked black pepper, olive oil, and fresh lemon juice. Mix well until blended.

Arrange Lobster Tails: Place butterflied lobster tails in a roasting pan. Drizzle the marinade over each tail and dot with unsalted butter.

Broil: Slide the roasting pan into the oven. Broil the lobster tails for about 10-11 minutes until the meat turns opaque and reaches 145°F.

Prepare Sauce: Collect the drippings from the pan in a small saucepan. Add the remaining butter and heat until melted.