Crumbled crackers often top this casserole, but we prefer homemade breadcrumbs because they soak up more butter.
Whatever name you give it, or however you serve it, it will remain a favorite decadentChristmas tradition.
Melt 2 tablespoons of the butter in a skillet over medium-high.
Credit: Greg DuPree
Add onion, bell pepper, celery, scallions, and garlic.
Cook, stirring, until vegetables soften, 5 to 7 minutes.
Add oysters and mushrooms.
Bring to a simmer, and cook, stirring often, 5 minutes.
Melt 1 tablespoon of the butter in a small saucepan over medium.
Whisk in flour, and cook, whisking constantly, until smooth, 30 seconds to 1 minute.
Add cream, and cook, whisking constantly, until very thick and beginning to bubble.
Add Parmesan, and cook, whisking constantly, until cheese is melted.
Using a fine wire-mesh strainer, strain oyster mixture; discard liquid.
Add oyster mixture to cheese sauce; stir until fully incorporated.
Stir in salt, pepper, and nutmeg.
Spread mixture in a lightly greased (with cooking spray) 11- x 7-inch baking dish.
Melt remaining 2 tablespoons of butter; toss breadcrumbs with melted butter.
Sprinkle breadcrumbs over oyster mixture.
