Preheat oven to 350°F

Saute onions, celery, and carrots in butter in a large skillet over medium heat until tender

Add flour and stir until smooth

Cook 1 minute stirring constantly

Add chicken broth and evaporated milk

Cook stirring occasionally until thickened and bubbly

Stir in chicken, peas, salt and pepper

Shape bottom pie crust

Add the filling. cover with top crust

Pinch edges of the 2 crusts together and then flute or crimp

Make a few slits in the top crust for the steam to escape

Bake uncovered for 30 minutes at 350°F

Then bake covered with foil for 30 more minutes

Let stand 10 minutes before serving