For the coral sauce: Peel the tails of the prawns while keeping the heads on. Heat some oil in a saute pan. Cook the shrimp for 3 to 4 minutes. Remove and set aside. Add the gray shrimp to the pan and cook for 1 minute. Reserve with the prawns. Rinse and dry the cuttlefish fillets. Cut it in pieces. Puree the prawns with the gray shrimp, cuttlefish, preserved lemon, 1/4 cup of the lobster stock and the lemon juice. Season the sauce with salt and pepper and then add the Espelette. Check the consistency, and adjust it with the remaining 1/4 cup lobster stock. Puree until the sauce is homogenous, 5 minutes. Pass the sauce through a fine mesh strainer. Check the seasoning and the consistency. Reserve.
For the gamberoni: Shell the tail of the prawns while keeping the heads on, and leaving the tail shell in place. Store in a cool place.
For the vegetables: Peel the carrots, and cut into 8 pieces. Peel the fennel. Wash the zucchini, remove top and tail. Cut the asparagus lengthwise into 2-inch pieces. Use a vegetable peeler to remove the hard outer skin. Wash and dry. Peel the red onions and rhubarb. Cut all of the vegetables using a mandolin into 1/2-inch-thick slices.
Clean the scallions, removing their outer skin. Thinly slice. Cut each of the tomatoes into 3 petals.
Remove the larger leaves of the lettuce. Cut the heart into 1/2-inch-thick slices. Reserve all of the vegetables.
Cooking the gamberoni: Heat a drizzle of olive oil in a saute pan. Sear the prawns on each side, coloring them slightly. Cook for 6 to 8 minutes, depending on their thickness. Drain and keep warm.
Cooking the vegetables: In a saute pan, heat a dash of olive oil. Add the carrots and sweat for 1 minute, then wet with a little bit of broth. Cover and cook. Add the fennel. Cook for 1 minute. Add the onions and asparagus. Cook for another minute. Add the spring onions and rhubarb. Cook for 1 minute, covered, over low heat. Eventually add a little bit of broth while the vegetables cook. Keep covered.
Uncover and add the arugula and the fava beans. All the vegetables must remain crisp. Adjust the seasoning. Add the tomato petals. Mix gently.
Finishing touches and presentation: Season the lettuce slices with a touch of olive oil, lemon juice and salt. Place in the bottom of the plates. Place the shrimp on top. Then place the vegetables. Finish with large drops of the coral sauce.