Preheat the grill to high. Place the langoustines in a shallow roasting tin and dot the butter on top.
Grill the langoustines for 2-3 minutes each side.
Meanwhile, mix together the garlic, mayonnaise, lemon zest and parsley.
Remove the langoustines from the grill and sprinkle with lemon juice, then serve with the mayonnaise and lemon wedges to squeeze over.
Cook's tip: Although perfect as a romantic starter for 2, this could easily be multiplied for a special dinner party. The lemon and parsley mayonnaise can be made in advance and stored in the fridge until ready to serve.