1 tablespoon chopped thyme and/or rosemary
Coarse salt and freshly ground pepper
1/2 cup fine yellow cornmeal
6 eggs, separated
1 cup freshly grated Parmesan cheese
1. Brown: Melt 4 tablespoons butter in a 12-inch skillet. Add mushrooms and cook, stirring, 10 minutes. Add onion and 3 cloves garlic. Cook, stirring, until mushrooms turn deep golden brown and all liquid has disappeared, about 12 minutes. Deglaze with sherry. Pull pan off heat, stir in green onions and thyme. Season with salt and pepper. Spread out mushrooms to cover the bottom of the skillet.
2. Thicken: Heat milk to a simmer in a large saucepan. Gradually whisk in cornmeal. Whisk over medium heat until thick, about 5 minutes. Pull pan off heat.
3. Bolster: Melt remaining 2 tablespoons butter with remaining garlic; whisk into thickened cornmeal mixture. Whisk in egg yolks, 2/3 cup Parmesan and 3/4 teaspoon salt.
4. Fluff: Beat egg whites to sturdy peaks. Stir one-quarter whites into the cornmeal mixture. Fold in the remaining whites.
5. Bake: Spread cornmeal mixture over mushrooms. Sprinkle with remaining Parmesan. Bake in a 350-degree oven until spoon bread is puffed and golden, about 20 minutes. Serve warm.