INGREDIENTS
•
1 small onion
•
1/2 pound mushrooms
•
2 tablespoons unsalted butter
•
1 tablespoon dry Sherry
•
1/2 teaspoon freshly grated nutmeg
•
a 17 1/4-ounce package frozen puff pastry sheets, thawed according to package directions
•
a chilled 14- to 17-ounce wheel Brie
•
1 large egg
•
Accompaniment: French bread slices or crackers