Thaw pastry sheets according to package directions.
On a lightly floured surface, overlap pastry sheets 1/2 inch to form a 14x12 inch rectangle; press edges firmly together to seal. Trim length of pastry to 2.5 inches longer than length of meat.
Spread mushroom mixture over top and sides of meat. Place meat in center of pastry. Fold pastry over meat; press edges together to seal. Decorate top with fancy-cut pastry trimmings, if desired.
Brush pastry with combined egg and water. Place meat in greased 15x10x1-inch jelly roll pan.
Bake 20 to 25 mins. or until pastry is golden brown. Let stand 10 mins. before slicing.
Enjoy! -Diana
Submitted by Diana Bogue Contributed on: and modified on Thursday May 6th, 2010