In a saucepan, melt butter over medium heat.
Add onions, carrots, potatoes and celery.
Cook until softened, about 5 to 7 minutes. Add salt, pepper, thyme, rosemary and a bay leaf and 1½ cups (375 mL) stock.
Blend flour into remaining stock, stir into saucepan.
Bring to boil and simmer 8 to 10 minutes, stirring until thickened.
Remove bay leaf; stir in peas and turkey.
Spoon into 9-inch (23 cm) pie crust.
Fit second pastry over top and seal edges and make vents in centre for steam to escape. Brush pastry with milk.
Bake at 400ºF for 10 minutes then reduce heat to 350ºF and bake for 20 to 25 minutes or until golden brown and filling is bubbly.
*If you are making this ahead of time to have on another night, refrigerate pie (until cold) before baking.
Cover with plastic wrap and refrigerate for up to 2 days or overwrap with heavy-duty foil and freeze for up to 2 weeks.
Thaw pie in refrigerator, and add 10 minutes to baking time.