Preheat your oven to 375°F (190°C).
Cook your turkey breast by simmering it in chicken stock with parsley, bay leaf, thyme, and peppercorns for about 25 minutes.
Let it cool and chop into bite-sized pieces.
Take a large saucepan and melt butter over medium heat.
Stir in flour until well blended to make a roux.
Gradually add reserved stock, stirring constantly until the mixture thickens.
Add carrots, turnips, and peas to the thickened stock mix.
Simmer until the vegetables are tender, then add the turkey pieces.
Season the mixture with salt and pepper to taste.
Prepare your pie crust by rolling it out and fitting it into your pie dish.
Spoon the filling mixture into the crust evenly.
Cover with another layer of pie crust on top, crimping the edges.
Brush the top crust with a beaten egg to enhance browning.
Cut a few slits in the crust for steam to escape.
Bake in the preheated oven for 30-35 minutes until the crust is golden brown.