Cook lobster tail; dice the lobster meat. Simmer white sauce with mushrooms, mustard, nutmeg and sherry. Toss lobster chunks with sauce and put this mixture back in the lobster shell. Top with breadcrumbs and Parmesan and place in 400-degree oven until golden brown, about 10 minutes.
2To steep the lobsters:lobster thermidor
2 1 1/2 to 2 pound lobsters
1/2 cup white vinegar per 8 quarts of water
enough water to completely cover lobsters
Place lobsters in a stockpot or other heat-proof container with a lid.
Bring water and vinegar to a rolling boil and then pour over lobsters and cover.
Let steep for 2 minutes for 1 1/2 pound lobsters and 3 minutes for 2 pound lobsters.
Remove from the pot with tongs, twist off claws with knuckles attached and return claws to pot for 5 minutes.
Twist off the tails from the body and pull off the flippers from the end of the tail.
Push the meat out through the large end of the tail. Remove the vein from the center of the tail.
After 5 minutes, remove the claws from the pot and crack open with the back of a knife. Use only enough force to crack the claw and loosen the meat.
Remove the meat from the knuckles. Reserve the tail shells and cut out the thin underside of them with scissors.