Ingredients (Serves 4-6)
- Preheat broiler. Melt 2 tbs of the butter in a skillet over medium-high. Add onion, celery, scallions, and garlic. Stirring, until vegetables soften, 5 to 7 minutes. Add oysters and mushrooms and remove from heat.
- Melt 1 tbs of the butter in a small saucepan over medium. Whisk in flour, and cook, whisking constantly, until smooth (approximately 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. Remove from heat.
- Using a fine 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 11×7-inch baking dish.
- Melt remaining 2 tablespoons of butter; toss breadcrumbs with melted butter. Sprinkle breadcrumbs over oyster mixture.
- Broil on middle rack of oven until breadcrumbs are deep golden brown and mixture is bubbly, 4 to 5 minutes