Heat butter in a large saucepan over medium heat. Add the onions, carrots, celery, and garlic and cook until soft. Do not allow them to obtain color.
Plunge a knife between the eyes of the lobsters to dispatch them. Then split them in half lengthwise, and remove the sand sack. Separate into tail, claw, and chest pieces and add the sections to the vegetables. Add 1/2-cup water and cover the pan with a lid for 4 minutes. Remove lid and allow the water to evaporate, then turn off the heat. Remove the lobster pieces from the pan and set aside. When cool enough to handle, remove the meat from the tails and claws, and reserve the meat.
Chop the shells into smaller pieces and return to the pan. Add the sherry and ignite. When the flames subside, add the wine and reduce by half. Add the water, parsley, cilantro, bay leaf, white peppercorns, poblano puree, and salt, to taste and cook over low heat for 20 minutes.
Remove most of the shells and pass the soup through a sieve into a clean medium saucepan, add the reserved lobster meat and cook until reduced to 2 cups. Blend the soup in a blender in batches then strain through a sieve into a clean, medium saucepan over medium low heat. Place the cream and milk in a small saucepan and reduce by half. Add the cream and cook until just heated through and season with honey, salt and pepper. Ladle into bowls and garnish with Toasted Corn Relish.
Preheat the oven to 400 degrees. Preheat grill to high. Remove ears from water. Roast corn for 10 minutes. Remove from the oven and grill in the husk for 15 to 20 minutes.
Peel the husk away, and cut corn away from the cob. Combine the corn kernels in a medium bowl with the red onion, roasted poblano, lime juice, olive oil, and tarragon. Season with salt and pepper, to taste.