1. To make crust: Combine flour, salt, basil and oregano in a large bowl. Cut in butter with pastry blender or two knives until mixture resembles coarse crumbs. Add water, 1 tablespoon at a time until dough can be formed into a ball. Divide dough in half and form each piece into a disk. Wrap in plastic wrap and chill in refrigerator for at least 25 minutes. For egg wash, whisk egg and water together in a small bowl; set aside.
2. To roast onion and garlic: Slice onion into 1/4-inch thick rounds and place on baking sheet lined with foil. Add peeled garlic cloves. Brush with olive oil. Broil 8 to 10 minutes or until charred. Let cool slightly before chopping.
3. To make filling: Heat butter in a large skillet over medium heat. Add roasted onion and garlic and cook 2 minutes. Stir in chicken broth, chicken, carrots, celery, peas, corn, parsley, salt, pepper, celery seed and ginger. Cook 6 minutes, stirring often. Whisk milk, corn starch and flour in a small bowl. Add to skillet, stirring until combined. Bring mixture to a boil, stirring frequently; boil two minutes. Remove from heat.
4. Preheat oven to 375°F.
5. To assemble pie: Roll half the dough for the crust into a 12-inch circle. (TIP: For easy handling, roll dough out between two sheets of lightly floured parchment paper.) Fit crust into 9-inch pie plate; press edge with a fork and brush edge with prepared egg wash. Spoon filling into crust. Roll remaining dough to a 9-inch circle and drape over filling. Press edges of crust together and trim any excess crust. Flute or press edges with a fork. Cut four vents in top crust; brush generously with egg wash.
6. Bake 40 to 45 minutes until top crust is golden brown. Cool 10 minutes on wire rack before serving.

*TIP: Save time and use meat from a rotisserie chicken for the roasted chicken.