Here's what you need:
2 lbs skinless, boneless chicken breasts, trimmed of fat
1 pkg (15 oz) refrigerated pie crusts
1/4 cup (1/2 stick) butter
1 large onion, finely chopped
3 Tbsp all purpose flour
1/2 tsp dried thyme
1 and 1/2 cups chicken broth
1/2 cup heavy cream
1 bag (16-20 oz) frozen peas & carrots
3/4 tsp salt
1/4 tsp black pepper
1 egg yolk
1 Tbsp water
Preheat oven to 425*. Place chicken in lg saucepan and add enough cool water to cover. Bring to a boil, reduce heat and simmer until just cooked through (about 10 minutes). Drain the chicken; let cool. Shred the chicken.
Meanwhile, fit one piecrust into a 9" pie plate and set asize. Roll the remaining pie crust out on a lightly floured surface. Cut crust into 1/2 inch wide strips with a pastry wheel and set aside.
Melt the butter in a lg saucepan over medium heat. Add the onion and cook, stirring, for 3 minutes. Whisk in the flour and the thyme and cook/stir for another 2 minutes. Add the brother and the cream and whisk until thickened (about 3-4 minutes). Remove from heat; stir in the shredded chicken, frozen veggies, salt & pepper.
Spoon filling into prepared pie plate. Arrange 6 of the piecrust strips inthe same direction on top of the pie, twisting the dough. Arrange the rest of the strips crosswise on top; fold edges under and pinch to seal.
Beat egg yolk and water. Brust the top of the pie with mixture. Place the pie on a baking sheet and bake until the crust is golden and filling is bubbly, about 45 minutes. Let stand for 10 minutes before serving.