Lobster and Butter Lettuce Salad

Bring a large pot three-fourths full of salted water to a boil over high heat. Add the lobster, headfirst. Cover and cook until the lobster is red, about 7 minutes. Transfer the lobster to a large bowl filled with ice water and let cool completely. Remove the meat from the claws, knuckles and tail, and discard the shells. Cut the meat into 1/2-inch pieces.

In a small bowl, whisk together the vinegar, mustard, half of the tarragon, salt and pepper. Add the olive oil in a slow, steady stream, whisking constantly until smooth and blended.

In a large bowl, combine the lettuce with about 2 Tbs. of the vinaigrette and gently toss to coat the lettuce evenly. Transfer the lettuce to a chilled platter.

In the same bowl, combine the lobster meat with about 1 Tbs. of the vinaigrette and gently toss to coat the lobster evenly. Scatter the lobster over the lettuce and garnish with the avocado and grapefruit. Sprinkle with the chives and the remaining tarragon and serve immediately. Pass the remaining vinaigrette alongside.