Melt 1½ T butter in a deep skillet or risotto pan. Add celery, carrots and onion; sauté until vegetables have softened slightly.
Add remaining butter to pan, then whisk in flour. Cook for 1 minute to remove any raw flour taste. Slowly add in broth, constantly whisking, then milk. Simmer until mixture has thickened to a gravy-like consistency. Add in turkey, corn and peas, cook together for 3-4 minutes. Set aside.
Preheat oven to 375.
Prepare crust for one of the methods mentioned above, making sure to cut vents in the top of the pie crust (not if you are using a machine). Brush crust with egg and bake for 25-30 minutes, until crust is crispy and golden.