Chicken Pot Pie

1 chicken, cooked and deboned
1 cup chopped onion
1 cup chopped celery
1 cup chopped carrots
1-2 cups chopped potatoes
1/3 cup margarine or butter
1/4 cup flour
2 cups chicken stock
1 cup half and half

Put margarine or butter in sautee pan and sautee veggies over medium low heat for 10 minutes. Add flour. Stir and cook one minute. Add chicken stock and half and half to veggies. Stir until thick and bubbly. About 10 minutes. Add chicken pieces. Pour in 9x13 pan. Top with pie crust. Cut slits in crust. Bake at 400 degrees for 30 minutes, or until crust in golden brown.