Cut the lobsters in half lengthwise and remove the stomach and the intestinal cord. Remove the meat from the shell and cut into slices, keeping the knife on the slant. Chop the shallot very finely. Put the white wine in a small saucepan and cook the shallot until it is tender and the wine reduced to half. Meanwhile, melt the butter and heat the meat very carefully in this. Add the shallot and wine mixture to the lobster meat with the sauce, mustard and pepper, mix and return to the shells. Sprinkle with grated cheese and brown under a hot grill.