The lobster can be cooked up to four hours ahead and kept refrigerated in an airtight container.
Cut 1/2 inch off the bottom (root end) of each head of endive. Separate the leaves, and set aside 24. Trim the leaves to measure about 4 inches in length. The leaves may be kept, in a single layer under a damp paper towel, in the refrigerator for up to 4 hours.
Bring a large pot of water to a rolling boil; add salt. Plunge lobsters in headfirst. Cover, allow water to return to a simmer, and cook for 6 minutes. Remove pot from heat. Leave lobsters in hot water for 3 more minutes. Remove lobsters, and let cool. Split lobsters lengthwise, and crack claws, allowing water to drain. Remove meat from shells, and cut into large chunks.
In a medium bowl, combine chives and dill with mayonnaise, lemon juice, and pepper to taste. Add celery and lobster meat, and mix well.
Place a tablespoon of the lobster salad on the base of each endive petal. Garnish with a sprig of chive, and serve.