Lobster, Endive and Mango Cocktail

Ingredients

 * ⅓ cup mayonnaise
 * ⅓ cup plain yogurt
 * 2 tbsp cognac
 * 1 tbsp ketchup
 * 1 tbsp fresh lemon juice, or to taste
 * salt and pepper to taste
 * 4 x 1½-pound lobsters
 * 3 mangos, firm and ripe
 * 1 cup celery, finely diced
 * 4 whole endives, plus 12 leaves for garnish
 * 3 tbsp minced fresh chives plus 24 whole chives for garnish

Directions

 * 1) In a small bowl whisk together mayonnaise, yogurt, cognac, ketchup, lemon juice, and salt and pepper then chill covered.
 * 2) Plunge the lobsters into a large kettle of boiling salted water and boil them, covered, for 10 minutes.
 * 3) Transfer the lobsters with tongs to a bowl and let them cool until they can be handled.
 * 4) Crack the shells, remove the meat, and cut it into ¾-inch pieces.
 * 5) Transfer the lobster meat to a large bowl and chill it, covered.
 * 6) The lobster cocktail may be prepared up to this point 1 day in advance.
 * 7) Halve the mangos by cutting just to the sides of each pit and, using a ¾-inch melon-ball cutter, scoop the flesh from the mango halves (about 2 cups).
 * 8) To the lobster meat add the mango balls, celery, whole endives, trimmed and sliced thin crosswise, the minced chives and sauce, then toss mixture until combined.
 * 9) Divide the lobster mixture among 12 chilled small glasses and garnish each serving with 1 of the endive leaves and 2 of the whole chives.