1. Fill a large pot with 1/2 inch of water. Stir in 2 teaspoons kosher salt and bring the water to a boil. Add the lobsters, cover with a tight-fitting lid and return the water to a boil. Once boiling, lower the heat to a gentle boil and cook the lobsters until they are bright red, about 12 minutes. Remove the lobsters, reserving the liquid. When the lobsters have cooled slightly, place them in a bowl and remove the meat from the claws and tail, again reserving any liquid that comes out of the shells. Chop the meat and refrigerate. Roughly chop the shells into small pieces and reserve, along with all the lobster remains.
2. Swirl the olive oil in a large pot over medium heat, then add the vegetables and herbs. Sweat until the onions are translucent, about 5 minutes, then increase the heat to medium-high and add the lobster shells and remains. Sauté for 5 to 6 minutes, then add the tomato paste and cook for an additional 3 to 4 minutes.
3. Add the sherry, then ignite or cook until the alcohol has evaporated. Add fish stock and 1 cup of the lobster-cooking liquid. Bring to a simmer and cook, covered, for 1 hour.
4. Strain the broth through a colander, pressing down hard on the solids to extrude as much liquid as possible. Wipe out the pot and pour in the broth. Add the rice and cook for at least 30 minutes, or until the grains are cooked to extreme softness.
5. Blend the bisque in a food processor or blender, then pass through a fine sieve, again pressing down hard on what solids remain. Add the cream and bring to a low simmer. Add the chopped lobster meat, let it heat through, then season to taste with salt and cayenne.