How to Make It
Fill a large stockpot with 2 inches of water, add the salt and bring to a boil over high heat. Put the lobsters in the boiling water, add the salt and bring to a boil over high heat. Put the lobsters in the boiling water, head first, and cook until they start to turn red, about 4 minutes. With tongs, transfer the lobsters to a bowl to cool.
Remove the meat from the knuckles and claws. Twist the tails off the bodies; reserve the greenish tomalley and blackish roe. Split the tails lengthwise lengthwise and and remove the meat. Pull out and discard the black intestinal vein. Cut the lobster meat into 1-inch chunks and transfer to a bowl.
In a small saucepan, melt 2 tablespoons of the butter with the sherry. Pour the butter over the lobster; set aside.
In a medium saucepan, melt the remaining 1 tablespoon of butter over moderately high heat. Stir in the flour to make a paste. Gradually whisk in the milk until smooth, then bring to a boil, whisking constantly. Simmer over low heat, whisking often, until the sauce is glossy and no floury taste remains, about 5 minutes. Add the cream and simmer for 2 minutes more. Fold in the lobster meat and sherry butter and season with pepper. Blend in the tomalley and roe and simmer until the lobster is cooked through, about 2 minutes longer. Serve with Hot Biscuits on the side.