Every recipe you’ll for this old buffet dish uses chopped frozen broccoli and cheddar, which makes you wonder why anyone would call it Rockefeller in the first place, even a mock one. While this version lacks the definitive Pernod/Ouzo/Anisette (nothing to keep you from adding a slash or so) it does have spinach and parsley, which seem to be the only ingredients that most deem essential for an honest oysters Rockefeller.
Sauté 4 cups chopped spinach with 1 bunch chopped green onions and a cup of chopped parsley in a stick of butter. Cool, add a cup of Parmesan, and about a half cup of crumbled bacon. Mix well, salt and pepper to taste. Remove stems from portabella caps; you can mince these and add them to the spinach mix if you like. Brush caps with olive oil, sprinkle with salt, and place on a baking sheet. Spoon spinach mixture on caps, top with more crumbled bacon and Parmesan, and bake at 350 until cheese is toasted.