Pastry:
3 cups (426 gm) white all purpose flour
1 tsp (5 ml) salt
3/4 cup + 1 tbsp (235 gm) butter or margarine
6 - 8 tbsp (90 - 120 ml) cold water
Filling:
3 boneless, skinless chicken breasts cut into 1" (2.5 cm) cubes
1/4 lb (115 gm) baby carrots (approx 3/4 cup)
2 sticks celery, chopped
1/4 lb (115 gm) frozen peas, thawed (approx 3/4 cup)
1 medium yellow onion, chopped
1 tbsp (15 ml) butter
1 tbsp (15 ml) olive oil
3 tbsp (45 ml) flour
1/2 tsp (3 ml) salt
1/4 tsp (1.5 ml) ground black pepper
1 tsp (5 ml) poultry seasoning
1 cup (250 ml) chicken stock
1/2 cup (125 ml) milk
Sift flour and salt together and cut in the margarine or butter till the mixture resembles coarse breadcrumbs. Add the water gradually, using a fork to combine the mixture into pastry dough. Wrap in plastic wrap and refrigerate until needed.
Preheat oven to 425°F or 220°C.
Place chicken chunks, carrots, and celery in a saucepan and add enough water to cover. Bring to a boil and simmer for 15 minutes. Drain, reserving liquid, stir in the frozen peas and set aside. Reserved liquid can be used to make chicken stock, if using instant chicken bouillon cubes or powder.
Cook onion in butter and oil over medium heat until soft and translucent and then stir in the flour and seasonings. Add chicken stock and milk and stir until thickened. Allow to cool.
Line a 10" (30 cm) diameter, deep pie plate or shallow casserole with pastry and add the chicken and vegetable mixture followed by the stock with onions. Add top crust, sealing edges with water and trim as desired, making a few slits for the steam to escape when baking.
Bake for 15 minutes and then reduce oven temperature to 350°F (180°C) and continue to bake for an additional 25 - 30 minutes.
Allow to cool for 10 minutes before serving.