To make the vinaigrette, combine the sugar and vinegars in a pot and caramelize over medium heat. When the liquid has caramelized, remove from heat. Let the pot cool, and add the hazelnut oil, truffle oil, mixed spices, and a pinch of fleur de sel and set aside.
To prepare the crustacean salad, clean the shells off and steam the clams and oysters. Once they are cooked, remove from the shell and add a pinch of fleur de sel and caramel vinaigrette. Mix until clam and oyster is lightly coated with vinaigrette and set aside.
To make the potato galette, slice the potatoes very thin. In a non-stick skillet arrange the potato slices each one overlapping the other in a circular fashion. Add a drizzle of olive oil and cook on both sides on medium heat. Both sides of the galette should be a golden brown color. Set aside for serving.
To prepare the langoustine, peel off the shells while still raw. In a skillet, add a little olive oil and slightly brown the langoustine, approximately 2 minutes. Remove the pan and place the langoustine in the oven to finish cooking for another 2 minutes.
To serve: Place the galette in the center of a plate. Stuff the zucchini flowers with the crustacean salad, and place on the side of the plate. On top of the galette, place a handful of mesclun greens also mixed with the vinaigrette. Add 4 langoustines to each plate surrounding the salad, and drizzle with vinaigrette and decorate with a sprig of parsley.