Clean the langoustines, remove the shells and the intestines.
Place the court-bouillon ingredients in a large, thick-bottomed pot. Bring to a simmer and cook for approximately 15 minutes. Bring the court bouillon to a boil and poach the langoustines for one minute. Cool the langoustines quickly, then chop the flesh. Combine with the egg whites and place in a bowl set over ice. Gradually incorporate the cream, beating vigorously until the mixture thickens and becomes homogenous. Adjust the seasoning. Shape the mixture into eight rolls (10 – 12 cm long). Wrap in plastic wrap and then aluminum foil. Poach for 3 minutes in simmering water. Cool and refrigerate.
Roughly chop cilantro and add to the olive oil. Heat to 70°C – 80°C; remove from the heat and infuse for 30 minutes. Strain through a china cap sieve and set aside.
Mango and ginger chutney:
Segment the grapefruit - cut a small slice off the top and bottom of the grapefruit. Stand it upright on a work surface and, following the contours of the fruit, use a small paring knife to cut away the skin and all the bitter white pith to expose the flesh. Cut away the segments (remove any seeds). Cut the mango, pineapple and grapefruit segments into small cubes. Heat the butter and oil in a sauté pan, add the mango, pineapple and grapefruit cubes, then add the unrefined cane sugar, Sherry vinegar, mango vinegar, ginger, currants and the curry powder. Cook for about 10 minutes or until soft. Adjust the seasoning as necessary with salt and Espelette pepper, then add the fresh cilantro.
Remove the aluminum foil and the plastic wrap from the langoustine rolls. Pat dry and roll each one in a half sheet of phyllo pastry brushed with olive oil. Heat a pan and a little olive oil, add the langoustine rolls and gently brown. Drain on paper towel. Cut each roll in three pieces.
Take a pastry brush and brush a line of cilantro oil on the plate. Place three langoustine rolls on top each roll with a quenelle of mango and ginger chutney, and a sprig of chervil. Decorate the plate with a line of Espelette pepper.