Pull pot roast into small pieces. Place beef in greased 9 x 13-inch baking pan. Add peas and carrots.
In a medium saucepan over medium heat, melt butter. Add flour and stir until well combine and mixture is bubbling.
Gradually whisk in au jus. Cook mixture for 5 minutes or until thickened and bubbly. Stir in pepper.
Add mixture to pot roast mixture; stir to combine.
Cover pot roast mixture with puff pastry, pressing the join together in center. Make about 12 small slits over pastry to allow steam to escape.
Brush pastry with egg. Bake for 45 to 50 minutes until pastry is golden brown and crisp.
2 lbs West Creek® beef pot roast, reduced-sodium, oven cooked, boneless
1 lb frozen carrots and peas, thawed
1 17.3 oz puff pastry sheet, thawed according to package directions