Place lobster in steamer or boil in water. Lobsters weighing up to 750g (1lb 10oz) should be cooked for 15 minutes, those weighing up to 1.25kg (2lb 12oz) for 20 minutes.
Place lobster on board, belly-side down, and cut in half along lengthwise, first through the middle of the head. Turn the lobster and
continue through its tail. Remove the white meat from the body and the intestinal tract from the tail meat. Break off the claws, crack
the shells and remove the meat without breaking it up too much.
Remove the green liver and any red roe from the head section and set aside. Discard the stomach sack. Clean the empty shells well.
Cut the meat into chunks. Return this and any roe back into the shells and place on a baking-sheet.
Melt the butter, add the shallots and cook until soft uncoloured. Add stock, Noilly Prat and half the cream. Bring to the boil, simmer until the mixture is reduced by three-quarters. End up with about 175ml (6fl oz) of liquid.
Add the remaining cream, bring to the boil, then simmer until the mixture has the consistency of a sauce. Whisk in the mustard, herbs and lemon juice. Mix and season.
Heat your grill to high. Spoon the sauce over the lobster meat in the shells then sprinkle the surface evenly with the Parmesan.
Grill for two to three minutes, or until the mixture is golden. Serve immediately