Preheat the grill to high.
Place split whole langoustines cut-side up onto a grill pan.
Spread a mixture of 50g butter and crushed garlic over the langoustines and season.
Grill the langoustines until the flesh is opaque.
Heat 25g butter and 15ml olive oil in a pan and cook the shelled langoustines for 5 minutes.
Add whisky to the pan and carefully ignite to flame for 1 minute.
Stir in crème fraîche and parsley, then season and keep warm.
Peel and grate the parboiled potatoes into a bowl.
Mix in the egg, seasonings, dill, lemon zest, juice, and 15ml olive oil.
Form the mixture into four cakes.
Fry cakes in remaining olive oil and butter for 5 minutes per side until golden.
Shake orange juice, lemon juice, vinegar, garlic, mustard, and sugar in a jar for the dressing.
Dress salad leaves first with rapeseed oil and then with the citrus dressing.
Serve a potato cake topped with sautéed langoustines and two grilled langoustines on the side with salad.