Step 1

Preheat oven to 400°F. Melt butter in a large heavy saucepan over medium-high. Add celery and onion, and cook, stirring often, until softened, about 6 minutes. Add flour, and cook, stirring constantly, 1 minute. Slowly stir in broth. Reduce heat to medium, and cook, stirring constantly, until mixture is thickened and bubbly. Stir in chicken, vegetables, hard-cooked eggs, salt, and pepper. Transfer mixture to a lightly greased 11- x 7-inch (2-quart) baking dish.

Step 2

Place the Pastry on a lightly floured surface, and roll out into a 1/8-inch-thick rectangle. Cut Pastry into 3/4-inch-wide strips, and arrange strips in a lattice design over the top of the chicken mixture. Lightly brush Pastry strips with beaten egg.

Step 3

Bake in preheated oven until golden brown and bubbly, 35 to 40 minutes.