Preheat your oven to 400°F (200°C).
In a large skillet, sauté the onions and celery until softened.
Add the mixed vegetables and cook for another 3-4 minutes.
Stir in the shredded chicken, thyme, salt, and pepper.
Pour in the chicken broth and heavy cream, simmering for 5 minutes.
Roll out the pie crusts and cut into circles to fit your mini pie pans.
Place the crusts in the pans and fill with the chicken mixture.
Cover with another crust, sealing the edges.
Brush the tops with the beaten egg.
Bake for 25-30 minutes or until golden brown.