Preheat the oven to 425°F (220°C).
In a saucepan, melt the butter over medium heat.
Whisk in the flour and cook for 1-2 minutes, stirring constantly.
Gradually pour in the chicken broth and milk, whisking continuously.
Stir in the shredded chicken, frozen vegetables, thyme, salt, and pepper.
Roll out the pie crusts and cut them into circles to fit your muffin tin.
Place the circular crusts into the muffin tin, pressing down gently.
Fill the crusts with the chicken and vegetable mixture.
Cover the filled pies with another piece of crust, sealing the edges.
Cut a few slits in the tops of the crusts to allow steam to escape.
Bake for 20-25 minutes or until the crust is golden brown.
Let the mini pot pies cool for a few minutes before serving.