Preheat oven to 400°F.
In a large saucepan, cook onion in hot butter and oil over medium heat for 15 minutes or until golden brown and very tender.
Stir in flour, sage, and thyme. Reduce heat to medium-low and cook and stir for 10 minutes or until the mixture is a light caramel color.
Whisk in chicken broth. Whisking continuously, bring mixture to boiling. Reduce heat and simmer 2 minutes.
Remove from heat. Stir in chicken and apple pie filling, and season with salt and black pepper; transfer to 3 quart round casserole and set aside.
Unroll pie crust onto a floured surface. Roll to 10-inch circle. Fold edges under and crimp edges to rim of casserole to seal. Cut small vents in the crust.
Bake for 30-35 minutes or until crust is golden brown. Let stand for 10 minutes before serving.