Preheat oven to 375° F. Let pie crust stand at room temperature according to package directions.
Dice carrot and chop onion.
Brown ground sirloin in a large skillet over medium heat. Drain and set aside.
Place carrot in a microwave dish. Add 1 tablespoon water; cover and cook on high for 2 minutes. Add frozen corn, and peas; microwave for 2 minutes. Drain.
To make filling, combine meat, vegetables, onion, Worcestershire sauce, black pepper and thyme in a bowl.
On a lightly floured surface, unroll pie crusts. Cut each pie crust into four pieces.
Spoon 1/4 cup of the filling onto half of each piece of piecrust. Lightly moisten pie crust edges with a small amount of milk or egg white.
Fold other half of pie crust over filling. Seal edges by crimping with a fork. Cut slits in the top of the pastries. Brush top with egg white. Place on a large, ungreased baking sheet.
Bake for 15 to 20 minutes or until crust is golden brown. Cool slightly on wire racks. Serve each pastie with 1 teaspoon ketchup.