1. Bring a large pot of water to a boil. Salt it lightly. Drop the lobsters headfirst into the boiling water. Cover, return to a boil, and cook for 2 minutes. Transfer the lobsters to a work surface. Using a clean kitchen towel to protect your hands, split the lobsters in half lengthwise with a long, sharp knife. Crack the claws.
2. Meanwhile, light a direct-heat charcoal fire and let it burn down to medium-hot (5 seconds to “ouch”) or preheat a gas grill to medium-high. Position the rack about 6 inches above the heat source. Preheat the oven to 400°F.
3. When the grill is ready, lay the lobsters, cut sides-up, on the rack. Cover and grill for 5 minutes. Turn the lobsters cut sides-down, cover, and continue to grill until the lobster meat is just cooked through while remaining moist, another 5 to 6 minutes.
4. Meanwhile, wrap the com tortillas in foil, dividing them into 2 packets. Heat them in the oven until supple and warm, about 10 minutes. Stir together the lime cream and the garlic in a small bowl.
5. Transfer the lobsters to plates. Serve, accompanied by the aioli and the tortillas. Encourage guests to use the tortillas to form small tacos, of lobster meat topped with the aioli.