Here's my recipe. I haven't made it, so I can't make any comments on how good it is.
Oysters Rockefeller
Yields: 24 oysters, about 4 servings
1 10 oz pkg frozen chopped spinach
24 oysters, in shell
2 T chopped onion
2 T parsley, chopped
2 T butter, melted
½ t salt
several drops Tabasco
dash of black pepper
shredded parmesan
rock salt
Cook spinach according to package directions. Drain well, press out excess water. To do this, place spinach in a towel you don’t mind staining. Fold corners together, and twist towel until all the water is squeezed from the spinach. Stir together the spinach, onion, parsley, the melted butter, salt, Tabasco, and a dash of black pepper. Store sauce in refrigerator.
Thoroughly wash each oyster shell. Open oysters, remove top shell, and cut oyster from bottom shell, leaving meat in the shell. Place the rock salt on an oven-proof plate or platter (a nacho platter works good for this.) . Place the oysters on top of the rock salt, pressing down to ensure they do not tip over. Turn you broiler on to it’s highest setting. Broil oysters for one minute, or until they just start to plump. Remove oysters, and top each oyster with one tablespoon of the sauce. Return oysters to heat. Cook one minute more, or until sauce starts to brown. Remove, and sprinkle parmesan cheese over each oyster. Return to broiler, and cook one more minute, until cheese is browned. Serve with oyster forks. Garnish with lemon wedges.