Grilled Lobster And Avocado Salad

* If the grapefruit vinegar is unavailable substitute 2 tablespoons grapefruit juice and 1 tablespoon white wine vinegar . If the grapefruit oil is unavailable substitute an equal amount of extra-virgin olive oil and add the grated zest of 1 grapefruit . In a medium bowl, whisk the mustard, shallots, vinegar and lime juice. Slowly whisk in the grapefruit oil and the extra-virgin olive oil. Do not worry if the dressing is not perfectly emulsified. Stir in the herbs , salt and pepper. Set the vinaigrette aside. Bring a large pot of salted water to boil. Preheat grill to high or preheat the broiler. Cut the avocado in half lengthwise. With a spoon carefully remove the avocado meat. Reserve the shells. Cut the avocado into 1/3-inch dice and place in a mixing bowl. Add lime juice and cover closely with plastic wrap . Remove the lobster meat from tail and parboil for 1 minute or until no longer translucent. Place lobster meat on the grill basting with butter just long enough to get a little grill flavor (about 1 minute per side). If cooking indoors, broil until lightly golden. Remove lobster from the grill and dice into approximately the same sized cubes as the avocado. In a large bowl, gently mix the avocado, lobster, red bell pepper, jicama and onion. Drizzle in half of the vinaigrette and carefully stir to mix evenly. Taste for seasoning and add more dressing or salt or pepper, as needed. Generously stuff the avocado shells. This can be prepared a few hours in advance and refrigerated. Place a bed of butter lettuce on chilled salad plates and place avocado half in center of plate. Scatter the lettuce with pine nuts, onion and tomatoes. Drizzle remaining vinaigrette over salad. Serve immediately.