Melt 3 tbsp butter in a medium pan over medium heat. Add 1 cup frozen mixed vegetables and saute until vegetables thaw and begin to soften. Season with salt, pepper, and garlic powder.
Add flour to vegetable mixture and stir to combine. Let cook 3-4 minutes then stir in chicken stock and Worcestershire.
Add shredded chicken and bring mixture to a boil. Reduce and let simmer 20 minutes with lid off.
Preheat oven to 375 and spray two ramekins with cooking spray and line a baking sheet with aluminum foil.
Roll pie crust dough out on floured surface and turn ramekins over on rolled out dough. Using a knife or dough cutter, cut a circle around the ramekin. Cut two small slits in the center of each circle (this will allow steam to escape). Set ramekins and pie crust aside.
Divide chicken pot pie filling between ramekins and top with pie dough. Melt remaining butter and brush over crust. Cut a small slit in the top of each pie and place ramekins on baking sheet. Sprinkle the top of each with a pinch of salt and fresh thyme, if using.
Bake 30-35 minutes until crust is browning and cooked through. Remove from oven and let cool 5-10 minutes before serving.