Allow the pie dough to come to room temperature. Once ready, place one portion of the pie crust into a 9-inch baking dish, gently pressing it into the edges and up the sides. Reserve the second portion of dough for the top crust.

Heat olive oil in a large pot over medium heat. Add the bite-sized pieces of chicken breast and sauté until the chicken is lightly browned at the edges, about 8 minutes.

To the browned chicken (from Step 2), add diced onion and minced garlic. Sauté for about 4 minutes until the onion softens. Add the frozen mixed vegetables and stir to combine with the chicken and aromatics.

Add the unsalted butter, flour, dried thyme, and dried sage to the pot with the chicken and vegetables. Stir until the vegetables and chicken are coated in the flour and spices. Slowly whisk in the chicken broth and Worcestershire sauce, ensuring the mixture becomes thick and creamy as the flour is absorbed. I find it helpful to add the broth gradually while stirring to avoid lumps.

Spoon the finished filling (from Step 4) into the prepared pie crust (from Step 1). Roll out the reserved top piece of dough and carefully place it over the filling. Trim any excess, seal the edges, and cut a few slits in the top crust to allow steam to escape.

Preheat the oven to 400°F. For a golden crust, optionally brush the top with a scrambled egg. Bake for 40-45 minutes until the crust is browned and the filling is bubbling. I like to let the pie sit for a few minutes before serving, so the filling sets up a bit.