Preheat the oven to 350 degrees F.
Grease a 2-quart baking dish with 1 tablespoon of butter.
Melt 2 tablespoons of the butter in a large skillet or sauté pan over medium-high heat. Add the green onions and garlic, and sauté for 1 minute. Add the mushrooms and sauté until they give off their liquid, 3 to 4 minutes. Add the oysters and their liquor, the parsley, Worcestershire sauce, lemon juice, salt, cayenne, and black pepper. Cook until the oysters just start to curl and are no longer opaque, and the liquor starts to evaporate, 3 to 5 minutes. Stir in the parsley and remove from the heat.
In a separate pan, melt 2 tablespoons of butter over medium heat. Saute the artichoke hearts until just warmed through. Remove from the heat and spread in an even layer to completely cover the bottom of the casserole.
In a separate pan, melt the remaining 3 tablespoons of butter over medium-high. Add the flour and stir constantly until thick, 2 minutes. Add the cream, and bring to a boil. Cook until thick, about 2 minutes. Remove from the heat and add to the oyster mixture, stirring to mix well. Stir in 1/4 cup of the cheese. Pour the mixture into the casserole on top of the artichoke hearts.
Sprinkle the seasoned bread crumbs over the top of the casserole, and top with the remaining 1/4 cup Parmesan cheese. Bake until the top is bubbly and has a golden crust, 15 to 25 minutes. (If necessary, broil for 3 minutes to brown the top evenly.) Serve hot.
Yield: 6 to 8 servings