Cook the chicken breasts by boiling or pan-searing them. Once cooked, shred or dice the chicken into bite-sized pieces. Set aside.
In a large pan, heat 2 tbsp olive oil over medium heat. Add the onion and garlic, sautéing for 2-3 minutes until softened and fragrant.
Add the mixed vegetables to the pan and cook for another 5 minutes, stirring occasionally.
Sprinkle the 2 tbsp flour over the vegetable mixture. Stir well to combine, allowing the flour to cook for 1-2 minutes to remove any raw taste.
Gradually pour in the 1 cup chicken broth while stirring constantly to avoid lumps. Add the ½ cup milk and continue stirring until the mixture thickens, about 5-7 minutes.
Add the cooked chicken to the vegetable mixture. Season with ½ tsp thyme, ½ tsp salt, and ¼ tsp pepper. Stir everything until well combined, and remove from heat.
Preheat your oven to 375°F (190°C).
Roll out your pie crust and fit it into a pie dish. Spoon the chicken and vegetable filling into the crust. Top with another crust if desired, crimp the edges, and cut a few slits on top for steam to escape.
Place the assembled pie in the oven and bake for 25-30 minutes, or until the crust is golden brown and the filling is bubbly
Let the pie cool for 5 minutes before slicing and serving. Enjoy your Healthy Chicken Pot Pie!