• 12 large button mushrooms (about 1 pound), wiped clean
• 4 tablespoons (½ stick) butter
• 1 tablespoon all-purpose flour
• ½ cup half-and-half
• 3 scallions (white part only), finely chopped
• ½ pound fresh claw crabmeat, picked over for shells and cartilage
• 2 tablespoons finely chopped pimentos
• 1 large egg, beaten
• Salt and freshly ground black pepper to taste
• 2 tablespoons butter, melted
• ¼ cup freshly grated Parmesan cheese

Preheat the oven to 375°F.

Remove stems from the mushrooms and chop finely, reserving the caps.

In a small saucepan, melt 1 tablespoon of the butter over moderate heat, add the flour, and whisk for 1 minute. Add the half-and-half, whisk till the sauce is smooth, and set aside.

In another medium saucepan, heat the remaining 3 tablespoons butter over moderate heat, add the chopped mushroom stems and the scallions, and cook, stirring, for 5 minutes. Add the crabmeat and pimentos and stir to blend. Add the white sauce, egg, and salt and pepper, stir till well blended, and set aside.

Arrange the mushroom caps hollow side down in a buttered baking dish. Brush with the melted butter, bake 10 minutes, and let cool. Stuff the mushroom cavities with equal amounts of the crabmeat mixture, sprinkle the tops with cheese, and bake till golden, about 20 minutes.