Drain and flake one 16-ounce can salmon.
Mix salmon with 1/3 cup mayonnaise; one 3-ounce can chopped mushrooms, drained; and 2 tablespoons crumbled blue cheese.
Toast and butter 8 slices of rye or white bread.
Spread toast with salmon mixture.
Sprinkle grated Parmesan cheese over sandwiches.
Broil 5 inches from heat till mixture is hot, about 6 to 7 minutes.