Finely chop garlic. Slice celery, carrots and onion into like-size pieces. Heat garlic with olive oil and 2 T butter over med-hi, adding celery, carrots and onion when pan is heated. Saute about 12 minutes, or until carrots are fairly tender but garlic and onions are not burned.
While vegetables are cooking, chop cooked chicken breasts and set aside.
Remove vegetables from pan and set aside. In same pan on med-hi, melt 1/2 c butter and stir in 1/2 flour. Brown mixture slightly, being careful not to let it burn. Add chicken stock a few ounces at a time, stirring to incorporate after each addition. Add wine to taste, then cream. Add spices to taste. (Probably don't need salt because of chicken stock.) Stir in cooked vegetables. Turn off heat and set aside.
Stir chicken and frozen peas into vegetable mixture and pour into pie. Place top crust on top and trim about 5/8" outside edge of dish. Fold top crust under bottom crust and flute (pinch) edge around pie to seal. Cut a small, simple design in top to let steam escape. (I make a three petal flower with stem, making sure none of the petals or stem touch each other.).
If making ahead of time, remove from fridge 1 hour before cooking (1/2 hour on a hot day) and don't brush with egg-white until just before cooking.
Preheat oven to 425 degrees. Brush top with egg white, cover edge with foil and bake for 5 minutes.
Then turn heat down to 350 degrees and remove foil. Continue baking for 35 - 45 minutes, or until crust appears done.
Let sit at least 10 minutes before slicing.