Fill a stockpot about two-thirds of the way full with water. Add a small amount of salt and bring to a full rolling boil on high heat. Add the frozen langoustines and boil for about 10 to 12 minutes or until the langoustines' shells turn a reddish pink.Remove the langoustines with a slotted spoon and allow to cool for at least 10 minutes.ill a stockpot about two-thirds of the way full with water. Add a small amount of salt and bring to a full rolling boil on high heat. Add the frozen langoustines and boil for about 10 to 12 minutes or until the langoustines' shells turn a reddish pink.