Preheat oven to 425 degrees F.
Mash together cheese, bread crumbs, and walnuts together with a fork; add pepper, to taste. Freeze mixture just until firm, about 10 minutes.
Scoop out center of bottom of each pear with large end of a melon-ball cutter, then continue to remove core to make a 1/4-cup cavity. Fill each cavity evenly with cheese mixture and seal bottom with a small piece of bread.
Roll out pastry 1/16-inch thick into a 15-inch square on a lightly floured surface with a floured rolling pin. Cut dough into quarters to make 4 equal pieces.
Stand 1 pear in center of a pastry square and brush pear all over with egg. Bring 1 corner of pastry up toward top of pear, pressing it against pear to adhere. Repeat with adjacent corner, then generously brush extending pastry fold with egg before pressing closely against side of the pear. Repeat process with remaining 2 corners. Fold top points of pastry 1/4-inch down and brush with egg. Transfer wrapped pear to a buttered large shallow (1-inch-deep) baking pan and chill while wrapping remaining pears (make sure pears are 5 inches apart in baking pan).
Chill wrapped pears 30 minutes.
Bake pears in middle of oven 20 minutes, or until fruit is just tender when pierced with a knife and pastry is golden and cooked through (pastry will shrink a bit). Cool pears at least 15 minutes before serving warm or at room temperature.