Fill the sink with cold water and add ice cubes. Bring a medium pot of salted water to a boil.
Meanwhile, numb the lobsters by placing them in the freezer for 30 minutes. Transfer them to a heavy cutting board, insert the tip of a large, heavy knife at the base of the heads, and cut completely through. Remove the claws, knuckles (the sections beneath the claws), and tails. Set the bodies aside for the broth. Cut the tails in half lengthwise up to the flat feathery appendages at the base of the tails (these remain intact) and reserve.
Transfer the claws to a large heatproof bowl, pour the boiling water over them to cover, and allow them to cook, about 5 minutes. After 3 minutes, add the knuckles. Remove the lobster parts and plunge into the ice water. When the lobster is cold, remove the mea tand reserve.
To make the broth, split the reserved lobster bodies. Heat a large, heavy pot over high heat. Add the oil and swirl to coat the bottom of the pot. When the oil shimmers, add the lobster bodies and saute, stirring, until the shells turn red, about 10 minutes. Add the tomato paste, fennel, onion, carrot, celery, lemongrass, and ginger and saute, stirring, until the vegetables are soft, about 8 minutes. Add the wine, stir, and reduce the liquid by half, 10 to 15 minutes. Do not boil; it will cloud the broth. Add the bay leaf, peppercorns, and about 8 cups of water to cover the bodies. Reduce the heat and simmer for 2 hours, strain, and keep hot.
Preheat the oven to 300 degrees F. To make the flans, heat a medium skilled over high heat. Add the oil and swirl to coat the pan. When the oil shimmers, add the shallots and saute, stirring, until soft, about 5 minutes. Add the mushrooms and saute, stirring, until softened, about 8 minutes. Transfer the mixture to a large bowl and place in the freezer to chill quickly, about 15 minutes. When cold, add the eggs, cream, scallions, and truffle oil and mix.
Fill a kettle with water and bring to a boil. Spray four 4-ounce ramekins lightly with nonstick cooking spray and have ready a baking dish large enough to hold them. Fill the ramekins four-fifths full with the flan mixture and transfer them to the pan. Add sufficient boiling water to the pan to come halfway up the sides of the ramekins and transfer to the oven. Bake just until the flans are set, about 25 minutes.
Meanwhile, season the reserved lobster tails with the salt and pepper to taste. Heat a large skillet over high heat. Add the canola oil and swirl to coat the pan. When the oil shimmers, add the tails, feeler sides down. Cook, turning once, until the shells turn red, about 5 minutes. Add the claws, stir, and add 3 cups of the broth. Add the lemon juice and season with the salt and pepper to taste.
Divide the fondue among 4 large pasta bowls. Carefully invert a flan onto each portion. Top with the lobster tail and claws and ladle the broth around. Garnish with the scallions and serve.
To make the fondue, heat a large skillet over medium heat. Add 1 tablespoon of the butter and swirl to coat the pan. Add the garlic and ginger and saute, stirring, until soft, about 5 minutes. Add the bok choy and 1/2 cup of the reserved lobster broth. Season with the salt and pepper to taste and cook until the bok choy is soft, about 5 minutes. Fold in the remaining 1 tablespoon of butter, correct the seasonings, and keep warm. Add the knuckles right before serving to warm.