Arnaud's Oysters Bienville

2/3 cup finely chopped mushrooms
1 teaspoon ground white pepper
4 tablespoons unsalted butter
1/2 cup brandy
1 1/2 teaspoons finely minced garlic
1/2 teaspoon cayenne
1 tablespoon finely chopped shallots
1 teaspoon salt
1/2 cup heavy cream
6 tablespoons grated Romano cheese
1 tablespoon flour
4 tablespoons dry bread crumbs
1/2 pound boiled shrimp, finely diced
1/4 cup finely minced parsley
2 dozen oysters on the half shell, drained
4 pans rock salt

In a large, heavy saucepan, saut